The Collaborative International Dictionary of English v.0.48:

Joe \Joe\, n.
   See Johannes.
   [1913 Webster]

The Free On-line Dictionary of Computing (30 December 2018):

joe

    A computer account whose user name and
   password are the same.  Joes are considered harmful, as are
   any passwords which are easy to guess.

   (1995-06-21)