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                                                                    EXHIBIT 10.1


                               AMENDMENT NO. 1 TO
                    AMENDED AND RESTATED EMPLOYMENT AGREEMENT

         THIS AMENDMENT NO. 1 TO AMENDED AND RESTATED EMPLOYMENT AGREEMENT (the
"Agreement") is made as of the 4th day of March, 1999, by and between Security
Dynamics Technologies, Inc., a Delaware corporation ("Employer"), and Charles R.
Stuckey, Jr. ("Employee").

         WHEREAS, Employer and Employee are parties to an Amended and Restated
Employment Agreement, dated as of November 1, 1997 (the "Agreement"); and

         WHEREAS, Employer and Employee are desirous of continuing Employee's
employment with Employer for the period, and on the terms and conditions, set
forth in the Agreement, subject to the amendment set forth herein;

         NOW, THEREFORE, in consideration of the foregoing and intending to be
bound, the parties hereby agree that Section 3(a) of the Agreement is amended
and restated in its entirety to read as follows:

         "(a)     Employee will occupy the position of Chief Executive Officer
                  of Employer. Employee will also be a member of the Employer's
                  Board of Directors (the "Board of Directors"), subject to the
                  terms of the Employer's Third Restated Certificate of
                  Incorporation as amended from time to time. Any subsequent
                  substantial diminution in the position, office or duties of
                  Employee (other than any such diminution resulting from a
                  Change in Control (as such term is defined in Section 12
                  hereof)) or material breach by the Employer of its obligations
                  under this Agreement shall be deemed a termination of this
                  Agreement other than "for cause" as defined in Section 9
                  hereof. Employee will report directly to the Board of
                  Directors and shall have such duties and responsibilities as
                  are set forth in the Employer's Amended and Restated By-Laws,
                  as amended from time to time, which duties and
                  responsibilities shall include, but not be limited to, overall
                  management responsibility for the operations and
                  administration of Employer as well as such other duties and
                  responsibilities, consistent with Employee's position as Chief
                  Executive Officer, as shall be defined by the Board of
                  Directors."

         Except as amended hereby, the Agreement shall remain unchanged and
shall remain in full force and effect. Capitalized terms used herein and not
otherwise defined shall have the respective meanings given to them in the
Agreement.


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         IN WITNESS WHEREOF, this Amendment No. 1 to Amended and Restated
Employment Agreement is executed as of the date first above written.

                                           EMPLOYER:

                                           SECURITY DYNAMICS TECHNOLOGIES, INC.



                                           /s/ Joseph B. Lassiter, III
                                           -------------------------------------
                                           Joseph B. Lassiter, III
                                           Director and Chairman of the
                                           Compensation Committee of the
                                           Board of Directors


                                           EMPLOYEE:



                                           /s/ Charles R. Stuckey, Jr.       
                                           -------------------------------------
                                           Charles R. Stuckey, Jr.