QuickLinks -- Click here to rapidly navigate through this document

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 8-K

CURRENT REPORT
PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): February 8, 2011

Kratos Defense & Security Solutions, Inc.
(Exact Name of Registrant as Specified in Charter)

Delaware
(State or Other Jurisdiction of
Incorporation)
  0-27231
Commission
File Number
  13-3818604
(I.R.S. Employer
Identification Number)

4820 Eastgate Mall, San Diego, CA 92121
(Address of Principal Executive Offices) (Zip Code)

Registrant's telephone number, including area code: (858) 812-7300

N/A
(Former Name, or Former Address, if Changed Since Last Report)

        Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

o
Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o
Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

ý
Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o
Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))


Item 1.01.    Entry into a Material Definitive Agreement.

        On February 8, 2011, Kratos Defense & Security Solutions, Inc. (the "Company") entered into an underwriting agreement (the "Underwriting Agreement") with Jefferies & Company, Inc., as representative for the several underwriters named in Schedule A thereto (the "Underwriters") relating to the sale and issuance by the Company of shares of the Company's common stock to the Underwriters in a firm commitment underwritten public offering in which Jefferies & Company, Inc. is serving as representative of the several Underwriters. Subject to the terms and conditions contained in the Underwriting Agreement, the Underwriters have agreed to purchase, and the Company has agreed to sell, 4,250,000 shares at the public offering price, less certain underwriting discounts and commissions (the "Offering"). The Company has also agreed to reimburse the Underwriters for certain of their out-of-pocket expenses.

        The shares of the Company's common stock are being offered and sold pursuant to a base prospectus dated August 21, 2009 and a prospectus supplement dated February 7, 2011 (together the "Prospectus Supplement"), pursuant to the Company's registration statement on Form S-3 (File No. 333-161340), which was declared effective by the SEC on August 21, 2009.

        Subject to the terms and conditions of the Underwriting Agreement, the Underwriters are committed to purchase and pay for all shares of the Company's common stock offered by the Prospectus Supplement, if any such shares are taken. However, the Underwriters are not obligated to take or pay for the shares of the Company's common stock covered by the Underwriters' over-allotment option described below, unless and until such option is exercised.

        The Company has granted the Underwriters an option, exercisable no later than 30 calendar days after the date of the Underwriting Agreement, to purchase up to an aggregate of 637,500 additional shares of the Company's common stock at the public offering price, less certain underwriting discounts and commissions. The Company will be obligated to sell these shares of common stock to the Underwriters to the extent the over-allotment option is exercised. The Underwriters may exercise this option only to cover over-allotments, if any, made in connection with the sale of the Company's common stock offered by the Prospectus Supplement. The Underwriters propose to offer the Company's common stock directly to the public at the offering price of $13.25 per share.

        The Company intends to use the net proceeds from the Offering to fund the cash consideration payable to the stockholders of Herley Industries, Inc. ("Herley") in connection with its proposed acquisition thereof. In the event that the acquisition of Herley is not completed, the Company will use the net proceeds from the Offering for general corporate purposes, including for the acquisition of or investment in other businesses, services and technologies that are complementary to its own and other general corporate expenses.

        The foregoing description of the Underwriting Agreement and the transactions contemplated thereby does not purport to be complete and is subject to, and qualified in its entirety by, the full text of the Underwriting Agreement, a copy of which is attached hereto as Exhibit 1.1 and the terms of which are incorporated herein by reference. The Underwriting Agreement contains customary representations, warranties and agreements by us, customary conditions to closing, indemnification obligations of the Company and the Underwriters, including for liabilities under the Securities Act of 1933, as amended, other obligations of the parties and termination provisions. The representations, warranties and covenants contained in the Underwriting Agreement were solely for the benefit of the parties to such agreement, and may be subject to limitations agreed upon by the contracting parties.

        A copy of the opinion of Paul, Hastings, Janofsky & Walker LLP relating to the legality of the issuance and sale of the Company's common stock in the Offering is attached as Exhibit 5.1 hereto.

Additional Information and Where to Find It

        No statement in this document or the attached exhibits is an offer to purchase or a solicitation of an offer to sell securities. The tender offer for the shares of Herley common stock has not commenced. The Company intends to file a tender offer statement on Schedule TO with the SEC, and Herley also



intends to file a solicitation/recommendation statement on Schedule 14D-9, with respect to the tender offer described in this Current Report on Form 8-K and the exhibits attached hereto. Any offers to purchase or solicitations of offers to sell will be made only pursuant to such tender offer statement. The tender offer statement (including an offer to purchase, a related letter of transmittal and other offer documents) and the related solicitation/recommendation statement will contain important information, including the various terms of, and conditions to, the tender offer, that should be read carefully by Herley's stockholders before they make any decision with respect to the tender offer. Such materials, when prepared and ready for release, will be made available to Herley's stockholders at no expense to them. In addition, at such time such materials (and all other offer documents filed with the SEC) will be available at no charge on the SEC's website: www.sec.gov and may also be obtained by directing a request to the Corporate Secretary of Kratos Defense & Security Solutions, Inc., at (858) 812-7300.

        The issuer has filed a registration statement (including a prospectus) and a preliminary prospectus supplement with the SEC for an underwritten public offering in connection with its proposed acquisition of Herley. Before you invest in such offering, you should read the preliminary prospectus supplement, including the base registration statement (and accompanying prospectus), and other documents the issuer has filed with the SEC for more complete information about the issuer and the offering. You may get these documents for free by visiting EDGAR on the SEC website at www.sec.gov. Alternatively, the issuer or any underwriter participating in the offering will arrange to send you the preliminary prospectus supplement and accompanying prospectus if you request them by calling toll-free (877) 547-6340.

Forward-Looking Statements

        Certain statements in this Current Report on Form 8-K may constitute "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. Such statements relate to a variety of matters, including but not limited to: the Underwriters' exercise of the over-allotment option; the Company's intended use of the net proceeds from the Offering; and other statements that are not purely statements of historical fact. These forward-looking statements are made on the basis of the current beliefs, expectations and assumptions of the management of the Company and are subject to significant risks and uncertainty. Investors are cautioned not to place undue reliance on any such forward-looking statements. All such forward-looking statements speak only as of the date they are made, and the Company undertakes no obligation to update or revise these statements, whether as a result of new information, future events or otherwise.

        Factors that could cause actual results to differ materially from those described in the forward-looking statements are set forth in the Prospectus Supplement.

Item 8.01    Other Events.

        On February 8, 2011, the Company issued a press release announcing the pricing of the Offering and the execution of the Underwriting Agreement. A copy of the press release is attached hereto as Exhibit 99.1 and is hereby incorporated by reference herein.

Item 9.01    Financial Statements and Exhibits.

(d)
Exhibits.

  1.1   Underwriting Agreement, dated February 8, 2011, between Kratos Defense & Security Solutions, Inc. and Jefferies & Company, Inc., as representative of the several underwriters named in Schedule A thereto.

 

5.1

 

Opinion of Paul, Hastings, Janofsky & Walker LLP

 

23.1

 

Consent of Paul, Hastings, Janofsky & Walker LLP (included in Exhibit 5.1)

 

99.1

 

Press release dated February 8, 2011


SIGNATURES

        Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

    Kratos Defense & Security Solutions, Inc.

 

 

By:

 

/s/ Eric DeMarco

Eric DeMarco
President and Chief Executive Officer

Date: February 8, 2011




QuickLinks

SIGNATURES

QuickLinks -- Click here to rapidly navigate through this document


Exhibit 1.1

4,250,000 SHARES

KRATOS DEFENSE & SECURITY SOLUTIONS, INC.

COMMON STOCK, PAR VALUE $0.001 PER SHARE

UNDERWRITING AGREEMENT

February 8, 2011

JEFFERIES & COMPANY, INC.
As Representative of the several Underwriters
c/o JEFFERIES & COMPANY, INC.
520 Madison Avenue
New York, New York 10022

Ladies and Gentlemen:

        Kratos Defense & Security Solutions, Inc., a Delaware corporation (the "Company"), proposes to issue and sell to the several underwriters named in Schedule A (the "Underwriters"), pursuant to the terms of this Underwriting Agreement (this "Agreement"), an aggregate of 4,250,000 shares (the "Firm Shares") of common stock, $0.001 par value per share (the "Common Stock"), of the Company. In addition, solely for the purpose of covering over-allotments, the Company proposes to grant to the Underwriters the option to purchase from the Company up to an additional 637,500 shares of Common Stock (the "Additional Shares"). The Firm Shares and, if and to the extent such option is exercised, the Additional Shares are hereinafter collectively referred to as the "Shares." The Shares are described in the Prospectus referred to below. Jefferies & Company, Inc. ("Jefferies") has agreed to act as representative of the several Underwriters (in such capacity, the "Representative") in connection with the offering and sale of the Shares.

        As part of the transactions described under the heading "Pending Acquisition of Herley Industries, Inc." in the General Disclosure Package, pursuant to a Merger Agreement (the "Merger Agreement") dated as of February 7, 2011, between the Company, Lanza Acquisition Co. ("MergerSub") and Herley Industries, Inc. ("Herley"), the Company intends to acquire Herley and its subsidiaries (the "Acquisition"). Immediately following consummation of the Acquisition, MergerSub will be merged with and into Herley with Herley to be the surviving entity.

        The Company and the Underwriters agree, severally and not jointly, as follows:

        1.    Sale and Purchase.    On the basis of the representations, warranties and agreements herein contained, and subject to the terms and conditions of this Agreement, the Company agrees to issue and sell to the several Underwriters an aggregate of 4,250,000 Firm Shares, and the Underwriters agree, severally and not jointly, to purchase from the Company the respective number of Firm Shares set forth opposite their names on Schedule A. The pricing terms of the purchase of the Firm Shares by the several Underwriters and the pricing terms of the offering of the Firm Shares to the public are as set forth in Schedule B hereto.

        In addition, the Company hereby grants to the Underwriters the option to purchase, and upon the basis of the warranties and representations and subject to the terms and conditions herein set forth, the Underwriters shall have the right to purchase, severally and not jointly, from the Company, all or a portion of the Additional Shares as may be necessary solely to cover over-allotments, if any, made in connection with the offering of the Firm Shares, at the same purchase price per share to be paid by the Underwriters to the Company for the Firm Shares. This option may be exercised by the Underwriters at any time and from time to time in whole or in part by written notice from the Representative to the Company, which notice may be given at any time within 30 days from the date of this Agreement. Such notice shall set forth (i) the aggregate number of Additional Shares as to which the option is being



exercised, (ii) the names and denominations in which the certificates will be delivered and (iii) the date, time and place at which such certificates will be delivered (such date, the "Additional Closing Date" and such time of such date, the "Additional Time of Purchase"); provided, however, that the Additional Time of Purchase may be simultaneous with, but shall not be earlier than the Time of Purchase (as defined below) and shall not be earlier than two nor later than five full business days after delivery of such notice of exercise. If any Additional Shares are to be purchased, each Underwriter agrees, severally and not jointly, to purchase the number of Additional Shares (subject to such adjustments to eliminate fractional shares as the Representative may determine) that bears the same proportion to the total number of Additional Shares to be purchased as the number of Firm Shares set forth on Schedule A opposite the name of such Underwriter bears to the total number of Firm Shares. The Representative may cancel the option at any time prior to its expiration by giving written notice of such cancellation to the Company.

        2.    Representations and Warranties of the Company.    The Company represents and warrants to, and agrees with, the Underwriters that:

2


3


4


5


6


7


8


9


10


        Any certificate signed by or on behalf of the Company and delivered to the Underwriters or to counsel for the Underwriters shall be deemed to be a representation and warranty by the Company to the Underwriters as to the matters covered thereby.

        3.    The Closing.    

        (a)   Payment of the purchase price for the Firm Shares shall be made to the Company by Federal Funds wire transfer against delivery of the certificates for the Firm Shares to the Underwriters through the facilities of The Depository Trust Company ("DTC") for the account of the Underwriters. Such payment and delivery shall be made at 10:00 A.M., New York time, on February 11, 2011 (the "Closing Date") (unless another time shall be agreed to by the Underwriters and the Company). The time at which such payment and delivery are to be made is hereinafter sometimes called the "Time of Purchase." Electronic transfer of the Firm Shares shall be made to the Underwriters at the Time of Purchase in such names and in such denominations as the Underwriters shall specify.

        It is understood that the Representative has been authorized, for its own account and the accounts of the several Underwriters, to accept delivery of and receipt for, and make payment of the purchase price for, the Firm Shares and any Additional Shares the Underwriters have agreed to purchase. Jefferies, individually and not as the Representative of the Underwriters, may (but shall not be obligated to) make payment for any Shares to be purchased by any Underwriter whose funds shall not have been received by the Representative by the Closing Date or the applicable Additional Closing Date, as the case may be, for the account of such Underwriter, but any such payment shall not relieve such Underwriter from any of its obligations under this Agreement.

        (b)   Payment of the purchase price for the Additional Shares shall be made at the Additional Time of Purchase in the same manner and at the same office and time of day as the payment for the Firm Shares. Electronic transfer of the Additional Shares shall be made to the Underwriters at the Additional Time of Purchase in such names and in such denominations as the Underwriters shall specify.

        (c)   Delivery of the documents required to be delivered to the Underwriters pursuant to Sections 4 and 6 hereof shall be at 10:00 A.M., New York time, on the Closing Date or the Additional Closing date, as the case may be, at the offices of White & Case, LLP, 1155 Avenue of the Americas, New York, New York 10036.

        4.    Further Covenants and Agreements of the Company.    The Company covenants and agrees with the Underwriters as follows:

11


12


13


14


        5.    Payment of Expenses.    The Company agrees to pay, or reimburse if paid by the Underwriters, whether or not the transactions contemplated hereby are consummated or this Agreement is terminated: (a) the costs incident to the authorization, issuance, sale and delivery of the Shares to the Underwriters and any taxes payable in that connection; (b) the costs incident to the registration of the Shares under the Securities Act; (c) the costs incident to the preparation, printing and distribution of the Registration Statement, the Base Prospectus, any Issuer Free Writing Prospectus, the General Disclosure Package, the Prospectus, any amendments, supplements and exhibits thereto or any document incorporated by reference therein; (d) the reasonable and documented fees and expenses incurred in connection with securing any required review by FINRA and any filings made with FINRA; (e) any applicable listing, quotation or other fees; (f) the fees and expenses (including, subject to the limitation set forth below, related fees and expenses of counsel for the Underwriters) of qualifying the Shares under the securities laws of the several jurisdictions as provided in Section 4(e) and of preparing, printing and distributing wrappers and blue sky memoranda; (g) all fees and expenses of the registrar and transfer agent of the Shares; and (h) all other costs and expenses of the Company and the Underwriters incident to the offering of the Shares by, or the performance of the obligations of, the Company and the Underwriters under this Agreement (including, without limitation, the fees and expenses of the Company's counsel, the Underwriters' counsel (subject to the limitation set forth below) and the Company's independent accountants and the travel and other reasonable expenses incurred by Company and the Underwriters' personnel in connection with any "road show" including, without limitation, any expenses advanced by the Underwriters on the Company's behalf (which will be promptly reimbursed)). Notwithstanding the foregoing provisions of this Section 5, the Company shall not be obligated to pay, or reimburse if paid by the Underwriters, legal costs and expenses incurred and payable by the Underwriters in excess of $100,000 and, with the exception of such legal costs and expenses, shall not be liable to the Underwriters for amounts in excess of $50,000 without prior written consent of the Company.

        6.    Conditions to the Obligations of the Underwriters, and the Sale of the Shares.    The obligations of the several Underwriters hereunder, and the closing of the sale of the Shares, are subject to the accuracy, when made and as of the Applicable Time and at the Time of Purchase and at any Additional Time of Purchase, as the case may be, of the representations and warranties of the Company contained herein, to the accuracy of the statements of the Company made in any certificates pursuant to the provisions hereof, to the performance by the Company of its obligations hereunder, and to each of the following additional terms and conditions:

15


16


17


        All opinions, letters, evidence and certificates mentioned above or elsewhere in this Agreement shall be deemed to be in compliance with the provisions hereof only if they are in form and substance reasonably satisfactory to counsel for the Underwriters.

        If any condition specified in this Section 6 is not satisfied when and as required to be satisfied, this Agreement may be terminated by the Representative by notice to the Company at any time on or prior to the Closing Date and, with respect to the Additional Shares, at any time on or prior to the applicable Additional Closing Date, which termination shall be without liability on the part of any party to any other party, except that Sections 5, 6, 7 and 9 shall at all times be effective and shall survive such termination.

18


        7.    Indemnification and Contribution.    

        (a)   The Company shall indemnify and hold harmless the Underwriters, each of its affiliates and each of its and their respective directors, officers, members, employees, representatives and agents and their respective affiliates, and each person, if any, who controls such Underwriters within the meaning of Section 15 of the Securities Act or Section 20 of the Exchange Act (collectively the "Underwriter Indemnified Parties," and each a "Underwriter Indemnified Party") against any loss, claim, damage, expense or liability whatsoever (or any action, investigation or proceeding in respect thereof), joint or several, to which such Underwriter Indemnified Party may become subject, under the Securities Act or otherwise, insofar as such loss, claim, damage, expense, liability, action, investigation or proceeding arises out of or is based upon (A) any untrue statement or alleged untrue statement of a material fact contained in any Issuer Free Writing Prospectus, any "issuer information" filed or required to be filed pursuant to Rule 433(d) of the Rules and Regulations, any Registration Statement or the Prospectus, or in any amendment or supplement thereto or document incorporated by reference therein, (B) the omission or alleged omission to state in any Issuer Free Writing Prospectus, any "issuer information" filed or required to be filed pursuant to Rule 433(d) of the Rules and Regulations, any Registration Statement or the Prospectus, or in any amendment or supplement thereto or document incorporated by reference therein, a material fact required to be stated therein or necessary to make the statements therein not misleading, or (C) any breach of the representations and warranties of the Company contained herein or failure of the Company to perform its obligations hereunder or pursuant to any law, and shall reimburse the Underwriter Indemnified Party promptly upon demand for any legal fees or other expenses reasonably incurred by such Underwriter Indemnified Party in connection with investigating, or preparing to defend, or defending against, or appearing as a third party witness in respect of, or otherwise incurred in connection with, any such loss, claim, damage, expense, liability, action, investigation or proceeding, as such fees and expenses are incurred; provided, however, that the Company shall not be liable in any such case to the extent that any such loss, claim, damage, expense or liability arises out of or is based upon an untrue statement or alleged untrue statement in, or omission or alleged omission from, any Registration Statement or the Prospectus, or any such amendment or supplement thereto, or any Issuer Free Writing Prospectus made in reliance upon and in conformity with written information concerning the Underwriters, or any of them, furnished to the Company by or on behalf of any Underwriter specifically for use therein, which information the parties hereto agree is limited to the Underwriters' Information. This indemnity agreement is not exclusive and will be in addition to any liability, which the Company may otherwise have and shall not limit any rights or remedies which may otherwise be available at law or in equity to each Underwriter Indemnified Party.

        (b)   The Underwriters shall indemnify and hold harmless the Company and its directors, its officers who signed the Registration Statement and each person, if any, who controls the Company within the meaning of Section 15 of the Securities Act or Section 20 of the Exchange Act (collectively the "Company Indemnified Parties" and each a "Company Indemnified Party") against any loss, claim, damage, expense or liability whatsoever (or any action, investigation or proceeding in respect thereof), joint or several, to which such Company Indemnified Party may become subject, under the Securities Act or otherwise, insofar as such loss, claim, damage, expense, liability, action, investigation or proceeding arises out of or is based upon (i) any untrue statement or alleged untrue statement of a material fact contained in any Issuer Free Writing Prospectus, any "issuer information" filed or required to be filed pursuant to Rule 433(d) of the Rules and Regulations, any Registration Statement or the Prospectus, or in any amendment or supplement thereto, or (ii) the omission or alleged omission to state in any Issuer Free Writing Prospectus, any "issuer information" filed or required to be filed pursuant to Rule 433(d) of the Rules and Regulations, any Registration Statement or the Prospectus, or in any amendment or supplement thereto, a material fact required to be stated therein or necessary to make the statements therein not misleading, but in each case only to the extent that the untrue statement or alleged untrue statement or omission or alleged omission was made in reliance upon and

19



in conformity with written information furnished to the Company by or on behalf of the Underwriters specifically for use therein, which information the parties hereto agree is limited to the Underwriters' Information, and shall reimburse the Company Indemnified Parties for any legal or other expenses reasonably incurred by such party in connection with investigating or preparing to defend or defending against or appearing as third party witness in connection with any such loss, claim, damage, liability, action, investigation or proceeding, as such fees and expenses are incurred. This indemnity agreement is not exclusive and will be in addition to any liability which the Underwriters might otherwise have and shall not limit any rights or remedies which may otherwise be available under this Agreement, at law or in equity to the Company Indemnified Parties.

        (c)   Promptly after receipt by an indemnified party under this Section 7 of notice of the commencement of any action, the indemnified party shall, if a claim in respect thereof is to be made against an indemnifying party under this Section 7, notify such indemnifying party in writing of the commencement of that action; provided, however, that the failure to notify the indemnifying party shall not relieve it from any liability which it may have under this Section 7 except to the extent it has been materially prejudiced by such failure; and, provided, further, that the failure to notify an indemnifying party shall not relieve it from any liability which it may have to an indemnified party otherwise than under this Section 7. If any such action shall be brought against an indemnified party, and it shall notify the indemnifying party thereof, the indemnifying party shall be entitled to participate therein and, to the extent that it wishes, jointly with any other similarly notified indemnifying party, to assume the defense of such action with counsel reasonably satisfactory to the indemnified party (which counsel shall not, except with the written consent of the indemnified party, be counsel to the indemnifying party). After notice from the indemnifying party to the indemnified party of its election to assume the defense of such action and approval by the indemnified party of counsel as set forth herein, except as provided herein, the indemnifying party shall not be liable to the indemnified party under Section 7 for any legal or other expenses subsequently incurred by the indemnified party in connection with the defense of such action other than reasonable costs of investigation; provided, however, that any indemnified party shall have the right to employ separate counsel in any such action and to participate in the defense of such action but the fees and expenses of such counsel (other than reasonable costs of investigation which shall remain the expense of the Company) shall be at the expense of such indemnified party unless (i) in the case of a Underwriter Indemnified Party, the employment thereof has been specifically authorized in writing by the Company in the case of a claim for indemnification under Section 7(a), or (ii) such indemnified party shall have been advised by its counsel that there may be one or more legal defenses available to it which are different from or additional to those available to the indemnifying party, or (iii) the indemnifying party has failed to assume the defense of such action and employ counsel reasonably satisfactory to the indemnified party within a reasonable period of time after notice of the commencement of the action or the indemnifying party does not diligently defend the action after assumption of the defense, in which case, if such indemnified party notifies the indemnifying party in writing that it elects to employ separate counsel at the expense of the indemnifying party, the indemnifying party shall not have the right to assume the defense of (or, in the case of a failure to diligently defend the action after assumption of the defense, to continue to defend) such action on behalf of such indemnified party and the indemnifying party shall be responsible for legal or other expenses subsequently incurred by such indemnified party in connection with the defense of such action; provided, however, that the indemnifying party shall not, in connection with any one such action or separate but substantially similar or related actions in the same jurisdiction arising out of the same general allegations or circumstances, be liable for the reasonable fees and expenses of more than one separate firm of attorneys at any time for all such indemnified parties (in addition to any local counsel), which firm shall be designated in writing by the Representative if the indemnified parties under this Section 7 consist of any Underwriter Indemnified Party or by the Company if the indemnified parties under this Section 7 consist of any Company Indemnified Parties. Subject to this Section 7(c), the amount payable by an indemnifying party under Section 7 shall include, but not be

20



limited to, (x) reasonable legal fees and expenses of counsel to the indemnified party and any other expenses in investigating, or preparing to defend or defending against, or appearing as a third party witness in respect of, or otherwise incurred in connection with, any action, investigation, proceeding or claim, and (y) all amounts paid in settlement of any of the foregoing. No indemnifying party shall, without the prior written consent of the indemnified parties, settle or compromise or consent to the entry of judgment with respect to any pending or threatened action or any claim whatsoever, in respect of which indemnification or contribution could be sought under this Section 7 (whether or not the indemnified parties are actual or potential parties thereto), unless such settlement, compromise or consent (i) includes an unconditional release of each indemnified party in form and substance reasonably satisfactory to such indemnified party from all liability arising out of such action or claim and (ii) does not include a statement as to or an admission of fault, culpability or a failure to act by or on behalf of any indemnified party. Subject to the provisions of the following sentence, no indemnifying party shall be liable for settlement of any pending or threatened action or any claim whatsoever that is effected without its written consent (which consent shall not be unreasonably withheld or delayed), but if settled with its written consent, or if its consent has been unreasonably withheld or delayed, or if there be a judgment for the plaintiff in any such matter, the indemnifying party agrees to indemnify and hold harmless any indemnified party from and against any loss or liability by reason of such settlement or judgment. In addition, if at any time an indemnified party shall have requested that an indemnifying party reimburse the indemnified party for reasonable fees and expenses of counsel, such indemnifying party agrees that it shall be liable for any settlement of the nature contemplated herein effected without its written consent if (i) such settlement is entered into more than forty-five (45) days after receipt by such indemnifying party of the request for reimbursement, (ii) such indemnifying party shall have received notice of the terms of such settlement at least thirty (30) days prior to such settlement being entered into and (iii) such indemnifying party shall not have reimbursed such indemnified party in accordance with such request prior to the date of such settlement.

        (d)   If the indemnification provided for in this Section 7 is unavailable or insufficient to hold harmless an indemnified party under Section 7(a) or Section 7(b), then each indemnifying party shall, in lieu of indemnifying such indemnified party, contribute to the amount paid, payable or otherwise incurred by such indemnified party as a result of such loss, claim, damage, expense or liability (or any action, investigation or proceeding in respect thereof), as incurred, (i) in such proportion as shall be appropriate to reflect the relative benefits received by the Company on the one hand and the Underwriters on the other hand from the Offering of the Shares, or (ii) if the allocation provided by clause (i) of this Section 7(d) is not permitted by applicable law, in such proportion as is appropriate to reflect not only the relative benefits referred to in clause (i) of this Section 7(d) but also the relative fault of the Company on the one hand and the Underwriters on the other with respect to the statements, omissions, acts or failures to act which resulted in such loss, claim, damage, expense or liability (or any action, investigation or proceeding in respect thereof) as well as any other relevant equitable considerations. The relative benefits received by the Company on the one hand and the Underwriters on the other with respect to such Offering shall be deemed to be in the same proportion as the total net proceeds from the Offering of the Shares purchased under this Agreement (before deducting expenses) received by the Company bear to the total compensation received by the Underwriters in connection with the Offering, in each case as set forth in the table on the cover page of the Prospectus. The relative fault of the Company on the one hand and the Underwriters on the other shall be determined by reference to, among other things, whether the untrue or alleged untrue statement of a material fact or the omission or alleged omission to state a material fact relates to information supplied by the Company on the one hand or the Underwriters on the other, the intent of the parties and their relative knowledge, access to information and opportunity to correct or prevent such untrue statement, omission, act or failure to act. The Company and the Underwriters agree that it would not be just and equitable if contributions pursuant to this Section 7(d) were to be determined by pro rata allocation or by any other method of allocation that does not take into account the equitable

21



considerations referred to herein. The amount paid or payable by an indemnified party as a result of the loss, claim, damage, expense, liability, action, investigation or proceeding referred to above in this Section 7(d) shall be deemed to include, for purposes of this Section 7(d), any legal or other expenses reasonably incurred by such indemnified party in connection with investigating, preparing to defend or defending against or appearing as a third party witness in respect of, or otherwise incurred in connection with, any such loss, claim, damage, expense, liability, action, investigation or proceeding. Notwithstanding the provisions of this Section 7(d), the Underwriters shall not be required to contribute any amount in excess of the total compensation received by the Underwriters hereunder less the amount of any damages which the Underwriters have otherwise paid or become liable to pay by reason of any untrue or alleged untrue statement, omission or alleged omission, act or alleged act or failure to act or alleged failure to act. No person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Securities Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation.

        8.    Default of One or More of the Several Underwriters.    If, on the Closing Date or the applicable Additional Closing Date, as the case may be, any one or more of the several Underwriters shall fail or refuse to purchase Shares that it or they have agreed to purchase hereunder on such date, and the aggregate number of Shares which such defaulting Underwriter or Underwriters agreed but failed or refused to purchase does not exceed 10% of the aggregate number of the Shares to be purchased on such date, the Representative may make arrangements satisfactory to the Company for the purchase of such Shares by other persons, including any of the Underwriters, but if no such arrangements are made by such Closing Date, the other Underwriters shall be obligated, severally and not jointly, in the proportions that the number of Firm Shares set forth opposite their respective names on Schedule A bears to the aggregate number of Firm Shares set forth opposite the names of all such non-defaulting Underwriters, or in such other proportions as may be specified by the Representative with the consent of the non-defaulting Underwriters, to purchase the Shares which such defaulting Underwriter or Underwriters agreed but failed or refused to purchase on such date. If, on the Closing Date or the applicable Additional Closing Date, as the case may be, any one or more of the Underwriters shall fail or refuse to purchase Shares and the aggregate number of Shares with respect to which such default occurs exceeds 10% of the aggregate number of Shares to be purchased on such date, and arrangements satisfactory to the Representative and the Company for the purchase of such Shares are not made within 48 hours after such default, this Agreement shall terminate without liability of any party to any other party except that the provisions of Sections 5, 6, 7 and 9 shall at all times be effective and shall survive such termination. In any such case either the Representative or the Company shall have the right to postpone the Closing Date or the applicable Additional Closing Date, as the case may be, but in no event for longer than seven days in order that the required changes, if any, to the Registration Statement and the Prospectus or any other documents or arrangements may be effected.

As used in this Agreement, the term "Underwriter" shall be deemed to include any person substituted for a defaulting Underwriter under this Section 8. Any action taken under this Section 8 shall not relieve any defaulting Underwriter from liability in respect of any default of such Underwriter under this Agreement.

        9.    Absence of Fiduciary Relationship.    The Company acknowledges and agrees that:

22


        10.    Successors; Persons Entitled to Benefit of Agreement.    This Agreement shall inure to the benefit of and be binding upon the Underwriters, the Company, and their respective successors and assigns. Nothing expressed or mentioned in this Agreement is intended or shall be construed to give any person, other than the persons mentioned in the preceding sentence, any legal or equitable right, remedy or claim under or in respect of this Agreement, or any provisions herein contained, this Agreement and all conditions and provisions hereof being intended to be and being for the sole and exclusive benefit of such persons and for the benefit of no other person; except that the representations, warranties, covenants, agreements and indemnities of the Company contained in this Agreement shall also be for the benefit of the Underwriter Indemnified Parties and the indemnities of the Underwriters shall be for the benefit of the Company Indemnified Parties. It is understood that the Underwriters' responsibility to the Company is solely contractual in nature and the Underwriters do not owe the Company, or any other party, any fiduciary duty as a result of this Agreement.

        11.    Survival of Indemnities, Representations, Warranties, Etc.    The respective indemnities, covenants, agreements, representations, warranties and other statements of the Company and the Underwriters, as set forth in this Agreement or made by them respectively, pursuant to this Agreement, shall remain in full force and effect, regardless of any investigation made by or on behalf of the Underwriters, the Company or any person controlling any of them and shall survive delivery of and payment for the Shares. Notwithstanding any termination of this Agreement, the indemnity and contribution agreements contained in Section 7 and the covenants, representations, warranties set forth in this Agreement shall not terminate and shall remain in full force and effect at all times.

        12.    Notices.    All statements, requests, notices and agreements hereunder shall be in writing, and:

23


        13.    Definition of Certain Terms.    For purposes of this Agreement "business day" means any day on which the NASDAQ Stock Market is open for trading.

        14.    Governing Law, Agent for Service and Jurisdiction.    This Agreement shall be governed by and construed in accordance with the laws of the State of New York, including without limitation Section 5-1401 of the New York General Obligations Law. No legal proceeding may be commenced, prosecuted or continued in any court other than the courts of the State of New York located in the City and County of New York or in the United States District Court for the Southern District of New York, which courts shall have jurisdiction over the adjudication of such matters, and the Company and the Underwriters each hereby consent to the jurisdiction of such courts and personal service with respect thereto. The Company and the Underwriters each hereby consent to personal jurisdiction, service and venue in any court in which any legal proceeding arising out of or in any way relating to this Agreement is brought by any third party against the Company or the Underwriters. The Company and the Underwriters each hereby waive all right to trial by jury in any legal proceeding (whether based upon contract, tort or otherwise) in any way arising out of or relating to this Agreement. The Company agrees that a final judgment in any such legal proceeding brought in any such court shall be conclusive and binding upon the Company and the Underwriters and may be enforced in any other courts in the jurisdiction of which the Company is or may be subject, by suit upon such judgment.

        15.    Underwriters' Information.    The parties hereto acknowledge and agree that, for all purposes of this Agreement, the Underwriters' Information consists solely of the following information in the General Disclosure Package, the Prospectus and in the Registration Statement: the concession figure appearing in the first paragraph under the section entitled "Underwriting—Commission and Expenses" and the information contained in the second, third and fifth paragraphs relating to stabilization transactions under the section entitled "Underwriting—Price Stabilization, Short Positions and Penalty Bids."

        16.    Partial Unenforceability.    The invalidity or unenforceability of any section, paragraph, clause or provision of this Agreement shall not affect the validity or enforceability of any other section, paragraph, clause or provision hereof. If any section, paragraph, clause or provision of this Agreement is for any reason determined to be invalid or unenforceable, there shall be deemed to be made such minor changes (and only such minor changes) as are necessary to make it valid and enforceable.

        17.    General.    This Agreement constitutes the entire agreement of the parties to this Agreement and supersedes all prior written or oral and all contemporaneous oral agreements, understandings and negotiations with respect to the subject matter hereof. In this Agreement, the masculine, feminine and neuter genders and the singular and the plural include one another. The section headings in this Agreement are for the convenience of the parties only and will not affect the construction or interpretation of this Agreement. This Agreement may be amended or modified, and the observance of any term of this Agreement may be waived, only by a writing signed by the Company and the Underwriters.

        18.    Counterparts.    This Agreement may be signed in any number of counterparts, each of which shall be an original, with the same effect as if the signatures thereto and hereto were upon the same instrument and such signatures may be delivered by facsimile.

24


        If the foregoing is in accordance with your understanding of the agreement between the Company and the Underwriters, kindly indicate your acceptance in the space provided for that purpose below.

    Very truly yours,

 

 

KRATOS DEFENSE & SECURITY SOLUTIONS, INC.

 

 

By:

 

/s/ Deanna Lund

Name: Deanna Lund
Title: Executive Vice President and Chief Financial Officer

25


        The foregoing Underwriting Agreement is hereby confirmed and accepted by the Representative in New York, New York as of the date first above written.

JEFFERIES & COMPANY, INC.
Acting as Representative of the
several Underwriters named in
the attached
Schedule A.
   

By:

 

JEFFERIES & COMPANY, INC.

 

 

By:

 

/s/ Kamlesh Bhatia

Name: Kamlesh Bhatia
Title: Managing Director

 

 

26



SCHEDULE A

Underwriters
  Number of
Firm Shares
to be Purchased
 

Jefferies & Company, Inc. 

    2,125,000  

B. Riley & Co., LLC. 

    1,700,000  

Oppenheimer & Co., Inc. 

    170,000  

Noble Financial Group, Inc. 

    170,000  

Imperial Capital, LLC

    85,000  
 

Total

    4,250,000  

27



SCHEDULE B

Pricing Information

Number of Shares to be Sold: 4,250,000

Public Offering Price: $13.25 per Share

Underwriting Discount: $0.6625 per Share

Proceeds to Company (before expenses): $12.5875 per Share

28



SCHEDULE C

List of Subsidiaries

1.
Kratos Government Solutions, Inc.

2.
Defense Systems, Incorporated

3.
JMA Associates, Inc.

4.
Madison Research Corporation

5.
Haverstick Consulting, Inc.

6.
HGS Holdings, Inc.

7.
Haverstick Government Solutions, Inc.

8.
DTI Associates, Inc.

9.
Rocket Support Services LLC

10.
Kratos Commercial Solutions, Inc.

11.
Kratos Mid-Atlantic, Inc.

12.
Kratos Southeast, Inc.

13.
Kratos Texas, Inc.

14.
WFI NMC Corp.

15.
Kratos Southwest L.P.

16.
SYS

17.
AI Metrix, Inc.

18.
Polexis, Inc.

19.
Reality Based IT Services, Ltd.

20.
Shadow I, Inc.

21.
Shadow II, Inc.

22.
Shadow III, Inc.

29


23.
DEI Services Corporation

24.
Digital Fusion, Inc.

25.
Digital Fusion Solutions, Inc.

26.
Summit Research Corporation

27.
Gichner Holdings, Inc.

28.
Gichner Systems Group, Inc.

29.
Gichner Systems International, Inc.

30.
Charleston Marine Containers Inc.

31.
Dallastown Realty I, LLC

32.
Dallastown Realty II, LLC

33.
Hammer Acquisition Inc.

34.
SCT Acqusition LLC

35.
Henry Bros. Electronics, Inc.

30



SCHEDULE D

List of officers and directors subject to Section 4(f)

Executive Officers

Eric DeMarco

Deanna Lund

Laura Siegal

Benjamin Goodwin

Directors

Scott Anderson

Bandel Carano

William Hoglund

Scot Jarvis

Samuel Liberatore

Jane Judd

31



SCHEDULE E

Free Writing Prospectus(es)

Herley Announcement and Q410 Pre-Announcement Conference Call Script, filed on February 7, 2011.

Press Release, Kratos Defense & Security Solutions Announces Preliminary Fourth Quarter and Fiscal 2010 Financial Results, filed with the SEC on February 7, 2011.

Press Release, Kratos Defense & Security Solutions, Inc. to Acquire Herley Industries, Inc., filed with the SEC on February 7, 2011.

Pricing Term Sheet, filed with the SEC on February 8, 2011.

32



EXHIBIT A

Form of Lock-Up Agreement

JEFFERIES & COMPANY, INC.
As Representative of the several Underwriters
c/o JEFFERIES & COMPANY, INC.
520 Madison Avenue
New York, New York 10022

February     , 2011

        Re: Kratos Defense & Security Solutions, Inc.—Public Offering of Shares

Dear Sirs:

        In order to induce Jefferies & Company, Inc. ("Jefferies"), as representative of the several underwriters named in Schedule A to the underwriting agreement, to enter into a underwriting agreement with Kratos Defense & Security Solutions, Inc., a Delaware corporation (the "Company"), with respect to the public offering (the "Offering") of shares of the Company's common stock, par value $0.001 per share ("Common Stock"), the undersigned hereby agrees that for a period (the "lock-up period") of ninety (90) days following the date of the final prospectus supplement filed by the Company with the Securities and Exchange Commission in connection with such Offering (the "Prospectus Supplement"), the undersigned will not, without the prior written consent of Jefferies, directly or indirectly, (i) offer, sell, assign, transfer, pledge, contract to sell, or otherwise dispose of, any shares of Common Stock or securities convertible into or exercisable or exchangeable for Common Stock (including, without limitation, shares of Common Stock or any such securities which may be deemed to be beneficially owned by the undersigned in accordance with the rules and regulations promulgated under the Securities Exchange Act of 1934, as the same may be amended or supplemented from time to time (such shares or securities, the "Beneficially Owned Shares")), (ii) enter into any swap, hedge or other agreement or arrangement that transfers in whole or in part, the economic risk of ownership of any Beneficially Owned Shares, Common Stock or securities convertible into or exercisable or exchangeable for Common Stock, or (iii) engage in any short selling of any Beneficially Owned Shares, Common Stock or securities convertible into or exercisable or exchangeable for Common Stock. The foregoing sentence shall not apply to (a) transactions relating to any Beneficially Owned Shares, Common Stock or securities convertible into or exercisable or exchangeable for Common Stock acquired in open market transactions after the completion of the Offering, (b) transfers of any Beneficially Owned Shares, Common Stock or securities convertible into or exercisable or exchangeable for Common Stock as a bona fide gift, (c) in the case of a natural person, transfers of any Beneficially Owned Shares, Common Stock or securities convertible into or exercisable or exchangeable for Common Stock by will or intestate succession or to any trust or partnership for the direct or indirect benefit of the undersigned or any member of the immediate family of the undersigned, (d) in the case of a non-natural person, distributions of any Beneficially Owned Shares, Common Stock or securities convertible into or exercisable or exchangeable for Common Stock to general or limited partners or stockholders or members of the undersigned, (e) in the case of a non-natural person, transfers of any Beneficially Owned Shares, Common Stock or securities convertible into or exercisable or exchangeable for Common Stock (A) in connection with the sale or other bona fide transfer in a single transaction of all or substantially all of the undersigned's capital stock, partnership interests, membership interests or other similar equity interests, as the case may be, or all or substantially all of the undersigned's assets, in any such case not undertaken for the purpose of avoiding the restrictions imposed by this Agreement or (B) to another corporation, partnership, limited liability company or other business entity so long as the transferee is an affiliate of the undersigned and such transfer is not for value, (f) in connection with the receipt or vesting of

33



securities issued to the undersigned by the Company pursuant to any equity incentive or other compensatory plans, the withholding by the Company or surrender of such securities and/or any sale or other disposition of such securities solely in order to satisfy tax liabilities with respect to such issuance or vesting or any deemed disposition or deemed sale with respect to such securities, provided that only one Form 4 shall be filed by or on behalf of the undersigned during the restricted period in connection with this clause (f), such Form 4 shall not be filed before [                  ], 2011 and no other filing shall be required or shall be voluntarily made during that period in connection with this clause (f), or (g) transfers pursuant to a sale or an offer to purchase 100% of the outstanding Common Stock, whether pursuant to a merger, tender offer or otherwise, to a third party or group of third parties; provided that in the case of any transfer or distribution pursuant to clause (b), (c), (d) or (e), each donee, pledgee, distributee or transferee shall sign and deliver a lock-up agreement substantially in the form of this Agreement; and provided, further, that , without derogating from the restrictions set forth in clause (f), no filing by any party under the Securities Exchange Act of 1934, as amended, shall be required or shall be voluntarily made during the lock-up period in connection with any transaction or transfer pursuant to clause (a), (b), (c), (d) or (e).

        For the purposes of this paragraph, "immediate family" shall mean spouse, domestic partner, lineal descendant (including adopted children), father, mother, brother or sister of the transferor.

        If (i) the Company issues an earnings release or material news or a material event relating to the Company occurs during the last seventeen days of the lock-up period, or (ii) prior to the expiration of the lock-up period, the Company announces that it will release earnings results during the sixteen-day period beginning on the last day of the lock-up period, the restrictions imposed by this Agreement shall continue to apply until the expiration of the eighteen-day period beginning on the issuance of the earnings release or the occurrence of the material news or material event.

        In addition, the undersigned hereby waives, from the date hereof until the expiration of the ninety (90) day period following the date of the Prospectus Supplement, any and all rights, if any, to request or demand registration pursuant to the Securities Act of 1933, as amended, of any shares of Common Stock or securities convertible into or exercisable or exchangeable for Common Stock that are registered in the name of the undersigned or that are Beneficially Owned Shares. In order to enable the aforesaid covenants to be enforced, the undersigned hereby consents to the placing of legends and/or stop transfer orders with the transfer agent of the Common Stock with respect to any shares of Common Stock, securities convertible into or exercisable or exchangeable for Common Stock or Beneficially Owned Shares.

        If (i) the Company notifies Jefferies in writing that it does not intend to proceed with the Offering, (ii) for any reason the Offering is terminated prior to the payment for and delivery of the Common Stock or (iii) the Offering shall not have been completed by February 28, 2011, then upon the occurrence of any such event, this Agreement shall immediately be terminated and the undersigned shall be released from its obligations hereunder.

[Signatory]

By:

       
   


   

Name:

       
   


   

Its:

       
   


   

34




QuickLinks

4,250,000 SHARES KRATOS DEFENSE & SECURITY SOLUTIONS, INC. COMMON STOCK, PAR VALUE $0.001 PER SHARE UNDERWRITING AGREEMENT
SCHEDULE A
SCHEDULE B Pricing Information
SCHEDULE C List of Subsidiaries
SCHEDULE D List of officers and directors subject to Section 4(f)
SCHEDULE E Free Writing Prospectus(es)
EXHIBIT A Form of Lock-Up Agreement

QuickLinks -- Click here to rapidly navigate through this document


Exhibit 5.1

[Paul Hastings Letterhead]

February 8, 2011

Kratos Defense & Security Solutions, Inc.
4820 Eastgate Mall
San Diego, California 92121

Ladies and Gentlemen:

        We have acted as counsel to Kratos Defense & Security Solutions, Inc., a Delaware corporation (the "Company"), in connection with the issuance and sale of up to an aggregate of 4,887,500 shares (the "Shares") of the Company's common stock, par value $0.001 per share, including up to 637,500 shares of common stock that may be sold pursuant to the exercise of an over-allotment option, pursuant to a Registration Statement on Form S-3 (File No. 333-161340) (the "Initial Registration Statement"), filed with the Securities and Exchange Commission (the "Commission") under the Securities Act of 1933, as amended (the "Act"), a Registration Statement on Form S-3 (File No. 333-172103) filed with the Commission pursuant to Rule 462(b) of the Act (the "462(b) Registration Statement," and together with the Initial Registration Statement, the "Registration Statements"), the prospectus dated August 21, 2009 (the "Base Prospectus") and the prospectus supplement to be filed with the Commission pursuant to Rule 424(b) under the Act (the "Prospectus Supplement"). The Base Prospectus and the Prospectus Supplement are collectively referred to as the "Prospectus".

        In connection with this opinion, we have examined originals or copies, certified or otherwise identified to our satisfaction, of such documents, resolutions, certificates and instruments of the Company, certificates of public officials, statutes, records and such other instruments and documents as we have deemed necessary or appropriate as a basis for the opinion set forth herein, including, without limitation: (i) the Registration Statements; (ii) the Prospectus; (iii) the Company's Amended and Restated Certificate of Incorporation, as amended, certified by the Secretary of State of the State of Delaware; and (iv) the Company's Amended and Restated Bylaws, certified by the Secretary of the Company.

        In addition, we have made such investigations of law as we have deemed necessary or appropriate as a basis for the opinion set forth herein.

        In our examination of the foregoing, we have assumed, without independent investigation or verification: (i) the genuineness of all signatures on all agreements, instruments and other documents submitted to us; (ii) the legal capacity and authority of all persons or entities executing all agreements, instruments and other documents submitted to us; (iii) the authenticity and completeness of all agreements, instruments, corporate records, certificates and other documents submitted to us as originals; (iv) that all agreements, instruments, corporate records, certificates and other documents submitted to us as certified, electronic, facsimile, conformed, photostatic or other copies conform to authentic originals thereof, and that such originals are authentic and complete; (v) the due authorization, execution and delivery of all agreements, instruments and other documents by all parties thereto; (vi) that the statements contained in the certificates and comparable documents of public officials, officers and representatives of the Company and other persons on which we have relied for the purposes of this opinion are true and correct; and (vii) that the officers and directors of the Company have properly exercised their fiduciary duties. As to all questions of fact material to this opinion and as to the materiality of any fact or other matter referred to herein, we have relied (without independent investigation) upon certificates or comparable documents of officers and representatives of the Company.

        Based upon the foregoing, and in reliance thereon, and subject to the limitations, qualifications and exceptions set forth herein, we are of the opinion that the Shares are duly authorized and upon



issuance, delivery and payment therefor in the manner contemplated by the Registration Statements and the Prospectus Supplement, will be validly issued, fully paid and nonassessable.

        Without limiting any of the other limitations, exceptions and qualifications stated elsewhere herein, we express no opinion with regard to the applicability or effect of the law of any jurisdiction other than, as in effect as of the date hereof, the Delaware General Corporation Law, the applicable provisions of the Delaware Constitution and reported judicial decisions interpreting these laws.

        This opinion deals only with the specified legal issues expressly addressed herein, and you should not infer any opinion that is not explicitly stated herein from any matter addressed in this opinion.

        We consent to the filing of this opinion as an exhibit to the Registration Statements and to the reference to our firm under the caption "Legal Matters" in the Prospectus Supplement. In giving such consent, we do not admit that we are within the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Commission thereunder.

Very truly yours,

/s/ Paul, Hastings, Janofsky & Walker LLP

2




QuickLinks


QuickLinks -- Click here to rapidly navigate through this document


Exhibit 99.1

LOGO   Press Contact:
Yolanda White
858-812-7302 Direct


FOR IMMEDIATE RELEASE
  Investor Information:
877-934-4687
investor@kratosdefense.com

KRATOS DEFENSE & SECURITY SOLUTIONS, INC. PRICES OFFERING OF
COMMON STOCK

        SAN DIEGO, CA, February 8, 2011—Kratos Defense & Security Solutions, Inc. (NASDAQ: KTOS), a leading national security solutions provider, announced today the pricing of an underwritten public offering of 4,250,000 shares of its common stock at a purchase price of $13.25 per share. The gross proceeds to the Company from this offering are expected to be $56,312,500, before deducting underwriting discounts and other estimated offering expenses. The Company has granted the underwriters a 30-day option to purchase up to an aggregate of 637,500 additional shares of common stock to cover overallotments, if any. All of the shares in the offering are to be sold by Kratos. The offering is expected to close on or about February 11, 2011, subject to customary closing conditions.

        The Company expects to use the net proceeds from this offering to fund the cash consideration payable to the stockholders of Herley Industries, Inc. (HRLY) in connection with its proposed acquisition of HRLY, pursuant to a cash tender offer. To the extent that the net proceeds are not applied to the HRLY acquisition, the Company intends to use them for general corporate purposes, including for the acquisition of or investment in other businesses, services and technologies that are complementary to those of the Company and other general corporate expenses.

        In connection with the offering, Jefferies & Company, Inc. is acting as sole book-running manager, B. Riley & Co., LLC is acting as lead manager and Oppenheimer & Co., Inc., Noble Financial Group, Inc. and Imperial Capital, LLC are acting as co-managers. A copy of the final prospectus supplement and accompanying prospectus relating to the offering, when available, may be obtained by contacting the Equity Syndicate Prospectus Department, Jefferies & Company, Inc., 520 Madison Avenue, 12th Floor, New York, NY, 10022 at (877) 547-6340 and at Prospectus_Department@Jefferies.com.

        Registration statements relating to the shares of common stock to be issued in the offering have been filed with the Securities and Exchange Commission (SEC) and are effective. This press release does not constitute an offer to sell, or the solicitation of an offer to buy, these securities, nor will there be any sale of these securities in any state or other jurisdiction in which such offer, solicitation or sale is not permitted.

About Kratos Defense & Security Solutions

        Kratos Defense & Security Solutions, Inc. (NASDAQ: KTOS) is a specialized national security business providing mission critical products, services and solutions for United States National Security priorities. Kratos' core capabilities are sophisticated engineering, manufacturing and system integration offerings for national security platforms and programs. Kratos' areas of expertise include C5ISR, unmanned systems, cyber warfare, cyber security, information assurance, critical infrastructure security and weapons systems sustainment. Kratos has primarily an engineering and technical oriented work force of approximately 2,800, the majority of which hold an active national security clearance. Kratos' primary end customers are United States Federal Government agencies, including the Department of Defense, classified agencies, intelligence agencies and Homeland Security related agencies.


Additional Information and Where to Find It

        This press release is neither an offer to purchase nor a solicitation of an offer to sell securities. The tender offer for the shares of HRLY common stock has not commenced. The Company intends to file a tender offer statement on Schedule TO with the SEC, and HRLY also intends to file a solicitation/recommendation statement on Schedule 14D-9, with respect to the tender offer described in this press release. Any offers to purchase or solicitations of offers to sell will be made only pursuant to such tender offer statement. The tender offer statement (including an offer to purchase, a related letter of transmittal and other offer documents) and the related solicitation/recommendation statement will contain important information, including the various terms of, and conditions to, the tender offer, that should be read carefully by HRLY's stockholders before they make any decision with respect to the tender offer. Such materials, when prepared and ready for release, will be made available to HRLY's stockholders at no expense to them. In addition, at such time such materials (and all other offer documents filed with the SEC) will be available at no charge on the SEC's Web site: www.sec.gov and may also be obtained by directing a request to the Corporate Secretary of Kratos Defense & Security Solutions, Inc., at (858) 812-7300.

Notice Regarding Forward-Looking Statements

        This news release contains certain forward-looking statements that involve risks and uncertainties, including, without limitation, statements regarding the completion, timing and size of the proposed public offering, Kratos' anticipated proceeds from the offering, its use of those proceeds and its intention to acquire HRLY. Actual results or developments may differ materially from those projected or implied in these forward-looking statements. Factors that may cause such a difference include, without limitation, risks and uncertainties related to market conditions and the satisfaction of customary closing conditions related to the proposed public offering. There can be no assurance that Kratos will be able to complete the proposed public offering on the anticipated terms, or at all. For a further discussion of risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to Kratos' business in general, see the risk disclosures in Kratos' SEC filings, including its most recent Annual Report on Form 10-K for the year ended December 27, 2009, its Quarterly Reports on Form 10-Q filed from time to time with the SEC, and in the final prospectus supplement related to the public offering to be filed with the SEC. All forward-looking statements included in this news release are based on information available at the time of the release. Kratos is under no obligation to (and expressly disclaims any such obligation to) update or alter its forward-looking statements, whether as a result of new information, future events or otherwise.




QuickLinks