<PAGE>
                                                                     EXHIBIT 4.1

                       AMENDMENT NO. 1 TO RIGHTS AGREEMENT

      THIS AMENDMENT NO. 1 TO RIGHTS AGREEMENT (this "AMENDMENT NO. 1"), dated
as of July 28, 2003, is made by and between N2H2, Inc., a Washington corporation
(the "COMPANY"), and Mellon Investor Services LLC, as Rights Agent (the "RIGHTS
AGENT"). Reference is made to the Rights Agreement dated as of May 24, 2002 (the
"RIGHTS AGREEMENT") between the parties. Capitalized terms used but not defined
herein shall have the respective meanings ascribed to them in the Rights
Agreement.

      WHEREAS, pursuant to Section 27 of the Rights Agreement, the Company and
the Rights Agent may from time to time supplement or amend the Rights Agreement
in accordance with the provisions of Section 27 thereof; and

      WHEREAS, the Company is a party to an Agreement and Plan of Merger (as it
may be amended or supplemented from time to time, the "SECURE COMPUTING MERGER
AGREEMENT"), dated July 28, 2003, among Secure Computing Corporation, a Delaware
corporation ("SECURE COMPUTING"), Nitro Acquisition Corp., a Washington
corporation and wholly owned subsidiary of Secure Computing ("MERGER SUB"), and
the Company, which provides for, among other things, the merger of Merger Sub
with and into the Company, with the Company as the surviving corporation (the
"SECURE COMPUTING MERGER"), subject to shareholder approval and other terms and
conditions; and

      WHEREAS, concurrently with the execution and delivery of the Secure
Computing Merger Agreement, Secure Computing and certain shareholders of the
Company (the "SHAREHOLDERS") entered into Voting Agreements, dated as of July
28, 2003 (the "VOTING AGREEMENTS"), which, among other things, obligate the
Shareholders to vote in support of the Secure Computing Merger, restrict the
ability of the Shareholders to transfer shares of the Company's Common Stock,
and grants Secure Computing an irrevocable proxy to vote the Shareholders'
shares of the Company's Common Stock; and

      WHEREAS, the Secure Computing Merger Agreement contemplates amendments to
the Rights Agreement so that the Rights Agreement will not be applicable to the
Secure Computing Merger Agreement, the Secure Computing Merger, the Voting
Agreements, and the transactions contemplated by the Merger Agreement and the
Voting Agreements; and

      WHEREAS, the Company's Board of Directors previously determined that it is
in the best interests of the Company and its shareholders to amend the Rights
Agreement as contemplated by the Secure Computing Merger Agreement.

      NOW, THEREFORE, in accordance with Section 27 of the Rights Agreement, the
Company and the Rights Agent hereby amend the Rights Agreement as follows:

      1. The definition of "ACQUIRING PERSON" in Section 1(a) of the Rights
Agreement is hereby modified and amended by adding the following sentence at the
end thereof:

            "Notwithstanding anything in this Agreement to the contrary, none of
            Secure Computing Corporation, a Delaware corporation ("SECURE
            COMPUTING"), Nitro Acquisition Corp., a Washington
<PAGE>
            corporation ("MERGER SUB"), or any of their Affiliates or
            Associates, shall be deemed to be an Acquiring Person by virtue of
            the execution of the Agreement and Plan of Merger, dated as of July
            28, 2003 (as the same may be amended from time to time, the "SECURE
            COMPUTING MERGER AGREEMENT"), by and among Secure Computing, Merger
            Sub and the Company, the Voting Agreements, dated as of July 28,
            2003, between Secure Computing and each of the directors and
            executive officers of the Company (the "VOTING AGREEMENTS") or the
            consummation of the transactions contemplated by the Secure
            Computing Merger Agreement, including, without limitation, the
            merger of Merger Sub with and into the Company (the "SECURE
            COMPUTING Merger"), or the acquisition of beneficial ownership of
            Common Shares pursuant to the Voting Agreements or the announcement
            of any of the foregoing transactions."

      2. Section 1(h) of the Rights Agreement is hereby modified and amended by
adding the following sentence at the end thereof:

            "Notwithstanding anything in this Agreement to the contrary, a
            Distribution Date shall not be deemed to have occurred as a result
            of the execution of the Secure Computing Merger Agreement or the
            Voting Agreements or the consummation of the transactions
            contemplated by the Secure Computing Merger Agreement, including,
            without limitation, the Secure Computing Merger, the acquisition of
            beneficial ownership of Common Shares pursuant to the Voting
            Agreements, or the announcement of any of the foregoing
            transactions."

      3. The definition of "FINAL EXPIRATION DATE" in Section 1(k) of the Rights
Agreement is hereby modified and amended to read as follows:

            "`FINAL EXPIRATION DATE' shall mean May 24, 2012 or, if earlier,
            immediately prior to the consummation of the Secure Computing Merger
            as contemplated by the Secure Computing Merger Agreement."

      4. The definition of "SECTION 13 EVENT" in Section 1(u) of the Rights
Agreement is hereby modified and amended by adding the following sentence at the
end thereof:

            "Notwithstanding anything in this Agreement to the contrary, a
            Section 13 Event shall not be deemed to have occurred as the result
            of the execution of the Secure Computing Merger Agreement or the
            Voting Agreements or the consummation of the transactions
            contemplated by the Secure Computing Merger Agreement, including,
            without limitation, the Secure Computing Merger, the acquisition of
            beneficial ownership of Common Shares pursuant to


                                       2
<PAGE>
            the Voting Agreements, or the announcement of any of the foregoing
            transactions."

      5. The definition of "SHARES ACQUISITION DATE" in Section 1(v) of the
Rights Agreement is hereby modified and amended by adding the following sentence
at the end thereof:

            "Notwithstanding anything in this Agreement to the contrary, a
            Shares Acquisition Date shall not be deemed to have occurred as a
            result of the execution of the Secure Computing Merger Agreement or
            the Voting Agreements or the consummation of the transactions
            contemplated by the Secure Computing Merger Agreement, including,
            without limitation, the Secure Computing Merger, the acquisition of
            beneficial ownership of Common Shares pursuant to the Voting
            Agreements, or the announcement of any of the foregoing
            transactions."

      6. The definition of "TRIGGERING EVENT" in Section 1(z) of the Rights
Agreement is hereby modified and amended by adding the following sentence at the
end thereof:

            "Notwithstanding anything in this Agreement to the contrary, a
            Triggering Event shall not be deemed to have occurred as a result of
            the execution of the Secure Computing Merger Agreement or the Voting
            Agreements or the consummation of the transactions contemplated by
            the Secure Computing Merger Agreement, including, without
            limitation, the Secure Computing Merger, the acquisition of
            beneficial ownership of Common Shares pursuant to the Voting
            Agreements, or the announcement of any of the foregoing
            transactions."

      7. Section 30 of the Rights Agreement is hereby modified and amended by
adding the following sentence at the end thereof:

            "Nothing in this Agreement shall be construed to give any holder of
            Rights (and, prior to the Distribution Date, the Common Shares) or
            any other Person any legal or equitable rights, remedies, or claims
            under this Agreement by virtue of the execution of the Secure
            Computing Merger Agreement or the Voting Agreements or the
            consummation of the transactions contemplated by the Secure
            Computing Merger Agreement, including, without limitation, the
            Secure Computing Merger, the acquisition of beneficial ownership or
            the transfer of Common Shares pursuant to the Voting Agreements, or
            the announcement of any of the foregoing transactions."

      8. This Amendment No. 1 shall be deemed to be a contract made under the
laws of the state of Washington and for all purposes shall be governed by and
construed in accordance with the laws of such state applicable to contracts to
be made and performed entirely within such


                                       3
<PAGE>
state; provided, however, that all provisions regarding the rights, duties and
obligations of the Rights Agent shall be governed by and construed in accordance
with the laws of the state of New York applicable to contracts to be performed
entirely within such state.

      9. This Amendment No. 1 may be executed in any number of counterparts,
each of which counterparts shall for all purposes be deemed to be an original,
and all of such counterparts shall together constitute but one and the same
instrument.

      10. In all respects not inconsistent with the terms and provisions of this
Amendment No. 1, the Rights Agreement is hereby ratified, adopted, approved and
confirmed. In executing and delivering this Amendment No. 1, the Rights Agent
shall be entitled to all of the privileges and immunities afforded to the Rights
Agent under the terms and conditions of the Rights Agreement.

      11. If any term, provision, covenant or restriction of this Agreement No.
1 is held by a court of competent jurisdiction or other authority to be invalid,
void or unenforceable, the remainder of the terms, provisions, covenants, and
restrictions of this Amendment No. 1, and of the Rights Agreement, shall remain
in full force and effect and shall in no way be affected, impaired or
invalidated.

                            [Signature page follows]


                                       4
<PAGE>
      IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 1 to
be duly executed, all as of the date and year first above written.

                                    N2H2, INC.

                                    By:      /s/  HOWARD PHILIP WELT
                                        -------------------------------
                                    Name:  Howard Philip Welt
                                    Title: President and Chief Executive Officer

                                    MELLON INVESTOR SERVICES LLC,
                                    as rights agent



                                    By:      /s/ THOMAS L. COOPER
                                        ----------------------------------------
                                    Name:  Thomas L. Cooper
                                    Title: Assistant Vice President