<PAGE>

                                                                   Exhibit 10.25

                                                                  EXECUTION COPY

                        AMENDMENT No. 5 and WAIVER dated as of December 31, 2000
                  (this "Amendment"), to the Credit Agreement dated as of June
                  23, 1999, as amended by Amendment No. 1 dated as of January
                  13, 2000, Amendment No. 2 dated as of March 29, 2000,
                  Amendment No. 3 dated as of June 30, 2000, and Amendment No. 4
                  and Waiver dated as of October 19, 2000 (the "Credit
                  Agreement"), among ANTEON INTERNATIONAL CORPORATION, a
                  Virginia corporation (the "Borrower"), the Lenders (as defined
                  in Article I of the Credit Agreement), CREDIT SUISSE FIRST
                  BOSTON, a bank organized under the laws of Switzerland, acting
                  through its New York branch, as an Issuing Bank (as defined in
                  Article I of the Credit Agreement), and as administrative
                  agent (in such capacity, the "Administrative Agent") for the
                  Lenders, MELLON BANK, N.A., a national banking association, as
                  syndication agent (in such capacity, the "Syndication Agent"),
                  as swingline lender (in such capacity, the "Swingline
                  Lender"), and as collateral agent (in such capacity, the
                  "Collateral Agent") for the Lenders, and DEUTSCHE BANK AG, New
                  York Branch, as documentation agent (in such capacity, the
                  "Documentation Agent").

      A. Pursuant to the Credit Agreement, the Lenders and the Issuing Banks
have extended, and have agreed to extend, credit to the Borrower.

      B. The Borrower has requested a limited waiver and amendment of the Credit
Agreement as set forth herein. The Required Lenders are willing to grant such
waiver and to amend the Credit Agreement on the terms and subject to the
conditions set forth herein.

      C. Capitalized terms used but not defined herein shall have the meanings
assigned to them in the Credit Agreement.

      Accordingly, in consideration of the mutual agreements herein contained
and other good and valuable consideration, the sufficiency and receipt of which
are hereby acknowledged, the parties hereto agree as follows:

      SECTION 1. Waiver. The Required Lenders hereby waive compliance by the
Borrower with the provisions of Section 6.08(b) of the Credit Agreement for the
fiscal year ending December 31, 2000, so long as the actual aggregate amount of
Capital Expenditures during such fiscal year does not exceed $6,700,000.

      SECTION 2. Amendments. (a) Section 6.01(j) of the Credit Agreement is
hereby amended by deleting the reference to "$500,000" and replacing it with the
reference to "$1,000,000".

            (b) Section 6.09 of the Credit Agreement is hereby amended by
replacing the table set forth therein with the following:

      Date or Period                                     Ratio
      --------------                                     -----

      December 31, 2000 through September 30, 2001       1.75:1.0

<PAGE>
                                                                               2


      October 1,2001 through December 31, 2001           2.00:1.0
      March 31, 2002 through December 31, 2002           2.25:1.0
      March 31, 2003 through December 31, 2003           2.50:1.0
      March 31, 2004 and thereafter                      3.00:1.0

      SECTION 3. Representations and Warranties. To induce the other parties
hereto to enter into this Amendment, the Borrower represents and warrants to
each of the Lenders, the Administrative Agent, the Issuing Banks, the Collateral
Agent, the Syndication Agent and the Documentation Agent that, after giving
effect to this Amendment, (a) the representations and warranties set forth in
Article III of the Credit Agreement are true and correct in all material
respects on and as of the date hereof, except to the extent such representations
and warranties expressly relate to an earlier date, and (b) no Default or Event
of Default has occurred and is continuing.

      SECTION 4. Amendment Fee. The Borrower agrees to pay to each Lender that
executes and delivers a copy of this Amendment to the Administrative Agent (or
its counsel) at or prior to 12:00 noon on March 30, 2001, an amendment fee (the
"Amendment Fee") in an amount equal to 0.25% of the sum of such Lender's
Revolving Credit Commitment (whether used or unused) and outstanding Term Loans,
in each case as of the Amendment Effective Date (as defined below). The
Amendment Fee shall be payable in immediately available funds on the Amendment
Effective Date. Once paid, the Amendment Fee shall not be refundable.

      SECTION 5. Effectiveness. This Amendment shall become effective as of the
date set forth above on the date (the "Amendment Effective Date") that the
following conditions are satisfied:

            (a) the Administrative Agent shall have received the Amendment Fee;
      and

            (b) the Administrative Agent shall have received counterparts of
      this Amendment that, when taken together, bear the signatures of the
      Borrower, the Guarantors and the Required Lenders.

      SECTION 6. Effect of Amendment. Except as expressly set forth herein, this
Amendment shall not by implication or otherwise limit, impair, constitute a
waiver of or otherwise affect the rights and remedies of the Lenders, the
Issuing Banks, the Collateral Agent, the Administrative Agent, the Syndication
Agent or the Documentation Agent under the Credit Agreement or any other Loan
Document, and shall not alter, modify, amend or in any way affect any of the
terms, conditions, obligations, covenants or agreements contained in the Credit
Agreement or any other Loan Document, all of which are ratified and affirmed in
all respects and shall continue in full force and effect. Nothing herein shall
be deemed to entitle any Loan Party to a consent to, or a waiver, amendment,
modification or other change of, any of the terms, conditions, obligations,
covenants or agreements contained in the Credit Agreement or any other Loan
Document in similar or different circumstances. This Amendment shall apply and
be effective only with respect to the provisions of the Credit Agreement
specifically referred to herein. After the date hereof, any reference to the
Credit Agreement shall mean the Credit Agreement, as modified hereby. This
Amendment shall constitute a "Loan Document" for all purposes of the Credit
Agreement and the other Loan Documents.

      SECTION 7. Counterparts. This Amendment may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when

<PAGE>
                                                                               3


so executed and delivered shall be deemed an original, but all such counterparts
together shall constitute but one and the same contract. Delivery of an executed
counterpart of a signature page of this Amendment by facsimile transmission
shall be as effective as delivery of a manually executed counterpart hereof.

      SECTION 8. Applicable Law. THIS AMENDMENT SHALL BE GOVERNED BY, AND
CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

      SECTION 9. Headings. The headings of this Amendment are for purposes of
reference only and shall not limit or otherwise affect the meaning hereof.

      SECTION 10. Expenses. The Borrower agrees to reimburse the Administrative
Agent for all out-of-pocket expenses in connection with this Amendment,
including the reasonable fees, charges and disbursements of Cravath, Swaine &
Moore, counsel for the Administrative Agent.

       SECTION 11. Acknowledgment of Guarantors. Each of the Guarantors hereby
acknowledges receipt and notice of, and consents to the terms of, this
Amendment.

<PAGE>
                                                                               4


            IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be duly executed by their duly authorized officers, all as of the date and year
first above written.


                                   ANTEON INTERNATIONAL CORPORATION,

                                   by:
                                       /s/ Carlton B. Crenshaw
                                      ------------------------------------------
                                      Name:  CARLTON B. CRENSHAW
                                      Title: SR. V.P. FINANCE AND ADMIN.


                                   ANTEON CORPORATION,

                                   by:
                                       /s/ Carlton B. Crenshaw
                                      ------------------------------------------
                                      Name:  CARLTON B. CRENSHAW
                                      Title: SR. V.P. FINANCE AND ADMIN.


                                   INTERACTIVE MEDIA CORP.,

                                   by:
                                       /s/ Carlton B. Crenshaw
                                      ------------------------------------------
                                      Name:  CARLTON B. CRENSHAW
                                      Title: VICE PRESIDENT


                                   CREDIT SUISSE FIRST BOSTON, individually
                                   and as Administrative Agent and Issuing Bank,

                                   by:

                                      ------------------------------------------
                                      Name:
                                      Title:

                                   by:

                                      ------------------------------------------
                                      Name:
                                      Title:


                                   MELLON BANK, NA., individually and as
                                   Collateral Agent, Swingline Lender and
                                   Syndication Agent,

                                   by:

                                      ------------------------------------------
                                      Name:
                                      Title:

<PAGE>
                                                                               4


            IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be duly executed by their duly authorized officers, all as of the date and year
first above written.


                                   ANTEON INTERNATIONAL CORPORATION,

                                   by:

                                      ------------------------------------------
                                      Name:
                                      Title:


                                   ANTEON CORPORATION,

                                   by:

                                      ------------------------------------------
                                      Name:
                                      Title:


                                   INTERACTIVE MEDIA CORP.,

                                   by:

                                      ------------------------------------------
                                      Name:
                                      Title:


                                   CREDIT SUISSE FIRST BOSTON, individually
                                   and as Administrative Agent and Issuing Bank,

                                   by:
                                      /s/ Robert Hetu
                                      ------------------------------------------
                                      Name:  ROBERT HETU
                                      Title: DIRECTOR

                                   by:
                                      /s/ Lalita Advani
                                      ------------------------------------------
                                      Name:  LALITA ADVANI
                                      Title: ASSISTANT VICE PRESIDENT


                                   MELLON BANK, NA., individually and as
                                   Collateral Agent, Swingline Lender and
                                   Syndication Agent,

                                   by:

                                      ------------------------------------------
                                      Name:
                                      Title:

<PAGE>
                                                                               4


            IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be duly executed by their duly authorized officers, all as of the date and year
first above written.


                                   ANTEON INTERNATIONAL CORPORATION,

                                   by:

                                      ------------------------------------------
                                      Name:
                                      Title:


                                   ANTEON CORPORATION,

                                   by:

                                      ------------------------------------------
                                      Name:
                                      Title:


                                   INTERACTIVE MEDIA CORP.,

                                   by:

                                      ------------------------------------------
                                      Name:
                                      Title:


                                   CREDIT SUISSE FIRST BOSTON, individually
                                   and as Administrative Agent and Issuing Bank,

                                   by:

                                      ------------------------------------------
                                      Name:
                                      Title:

                                   by:

                                      ------------------------------------------
                                      Name:
                                      Title:


                                   MELLON BANK, NA., individually and as
                                   Collateral Agent, Swingline Lender and
                                   Syndication Agent,

                                   by:
                                       /s/ David H. Reed
                                      ------------------------------------------
                                      Name:  DAVID H. REED
                                      Title: 1st VICE PRESIDENT

<PAGE>

                              Signature Page for Amendment No. 5 and Waiver
                              dated as of December 31, 2000 to the Anteon Credit
                              Agreement


                              SHERIKON, INC.


                              by:
                                   /s/ Carlton B. Crenshaw
                                  ----------------------------------------------
                                  Name:  Carlton B. Crenshaw
                                  Title: Senior Vice President, Finance and
                                         Administration


                              SOUTH TEXAS REPAIR, INC.


                              by:
                                   /s/ Carlton B. Crenshaw
                                  ----------------------------------------------
                                  Name:  Carlton B. Crenshaw
                                  Title: Senior Vice President, Finance and
                                         Administration


                              SHERIKON SPACE SYSTEMS, INC.


                              by:
                                   /s/ Carlton B. Crenshaw
                                  ----------------------------------------------
                                  Name:  Carlton B. Crenshaw
                                  Title: Senior Vice President, Finance and
                                         Administration


                              ANTEON - CITI, LLC


                              by:
                                   /s/ Curtis L. Schehr
                                  ----------------------------------------------
                                  Name:  Curtis L. Schehr
                                  Title: Vice President

<PAGE>

                              Signature Page for Amendment No. 5 and Waiver
                              dated as of December 31, 2000 to the Anteon Credit
                              Agreement

To Approve the Amendment:

Name of Institution:          Mellon Bank
                              --------------------------------------------------


                              by:
                                   /s/ David H. Reed
                                  ----------------------------------------------
                                  Name: David H. Reed
                                  Title: 1st Vice President

<PAGE>

                              Signature Page for Amendment No. 5 and Waiver
                              dated as of December 31, 2000 to the Anteon Credit
                              Agreement

To Approve the Amendment:

                              Transamerica Business Capital Corporation
                              (successor to Transamerica Business
                              Credit Corporation)


                              by: /s/ Stephen K. Goetschius
                                  ----------------------------------------------

                              Name: Stephen K. Goetschius
                              Title: Senior Vice President

<PAGE>

                              Signature Page for Amendment No. 5 and Waiver
                              dated as of December 31, 2000 to the Anteon Credit
                              Agreement

                              IBM Credit Corporation


                              by:
                                   /s/ Thomas S. Curcio
                                  ----------------------------------------------
                              Name:  Thomas S. Curcio
                              Title: Manager of Credit, Commercial and
                                      Specialty Financing

<PAGE>

                              Signature Page for Amendment No. 5 and Waiver
                              dated as of December 31, 2000 to the Anteon Credit
                              Agreement

To Approve the Amendment:

Name of Institution:          FLEET NATIONAL BANK
                              --------------------------------------------------


                              by:
                                   /s/ Roger C. Boucher
                                  ----------------------------------------------
                                  Name: Roger C. Boucher
                                  Title: Director

<PAGE>

                              Signature Page for Amendment No. 5 and Waiver
                              dated as of December 31, 2000 to the Anteon Credit
                              Agreement

To Approve the Amendment:

Name of Institution:
                              Deutsche Bank AG, New York Branch and/or
                              Cayman Islands Branch


                              by:
                                   /s/ David G. Dickinson, Jr.
                                  ----------------------------------------------
                                  Name: David G. Dickinson, Jr.
                                  Title: Vice President


                              by:
                                  /s/ Christopher A. Koch
                                  ----------------------------------------------
                                  Name: Christopher A. Koch
                                  Title: Vice President

<PAGE>

                              Signature Page for Amendment No. 5 and Waiver
                              dated as of December 31, 2000 to the Anteon Credit
                              Agreement

To Approve the Amendment:

Name of Institution:          Branch Banking & Trust Company
                              --------------------------------------------------


                              by:
                                  /s/ Ronald P. Gudbrandsen
                                  ----------------------------------------------
                                  Name: Ronald P. Gudbrandsen
                                  Title: Vice President
<PAGE>

                              Signature Page for Amendment No. 5 and Waiver
                              dated as of December 31, 2000 to the Anteon Credit
                              Agreement

To Approve the Amendment:

Name of Institution:          Bank Polska Kasa Opieki S.A.
                              --------------------------------------------------


                              by:
                                   /s/ Hussein B. El-Tawil
                                  ----------------------------------------------
                                  Name: Hussein B. El-Tawil
                                  Title: Vice President

<PAGE>

                              Signature Page for Amendment No. 5 and Waiver
                              dated as of December 31, 2000 to the Anteon Credit
                              Agreement

To Approve the Amendment:

Name of Institution:          The Bank of Nova Scotia
                              --------------------------------------------------


                              by:
                                   /s/ Todd S. Meller
                                  ----------------------------------------------
                                  Name:  TODD S. MELLER
                                  Title: MANAGING DIRECTOR
<PAGE>

                              Signature Page for Amendment No. 5 and Waiver
                              dated as of December 31, 2000 to the Anteon Credit
                              Agreement

To Approve the Amendment:

Name of Institution:          PNC BUSINESS CREDIT
                              --------------------------------------------------


                              by:
                                   /s/ Eric Huff
                                  ----------------------------------------------
                                  Name:  ERIC HUFF
                                  Title: ASSISTANT VICE PRESIDENT