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                                                                    EXHIBIT 10.3

                      SECURITY DYNAMICS TECHNOLOGIES, INC.

                                 AMENDMENT NO. 4

                                       TO

                             1994 STOCK OPTION PLAN


         The 1994 Stock Option Plan (the "Plan") of Security Dynamics
Technologies, Inc. is hereby amended as follows (capitalized terms used herein
and not defined herein shall have the respective meaning ascribed to such terms
in the Plan):

         A new Section 8A shall be inserted after Section 8 to read in its
entirety as follows:

         "8A.  DEFERRAL.

               An optionee who is a participant in a deferred compensation plan
         established by the Company may elect, with the permission of the Board
         of Directors and in accordance with rules established by the Board of
         Directors, to defer the receipt of any shares of Common Stock issuable
         upon the exercise of an option provided that such election is
         irrevocable and made at least that number of days prior to the exercise
         of the option which shall be determined by the Board of Directors. The
         optionee's account under such deferred compensation plan shall be
         credited with a number of stock units equal to the number of shares so
         deferred."

         Except as aforesaid, the Plan shall remain in full force and effect.


                          Adopted by the Board of Directors on January 22, 1998