Usage: SET SECURITY [ON|OFF|TOGGLE]
  This enabled some security measures in your client, depending on the
  settings of various bits.

        bit     value   purpose
         0        1     cannot use $vars as commands
         1        2     /exec may only be used interactively
         2        4     /set may only be used interactively

  The values are additive:

    /set secutory 3  --> $vars and /exec security
    /set security 6  --> /exec and /set security

  If set to 0, no security is enabled.
