dm is a program used to regulate game playing.
  dm expects to be invoked with the name of a game that
  a user wishes to play. This is done by creating symbolic links to
  dm, in the directory
  /usr/games for all of the regulated games. The actual
  binaries for these games should be placed in a “hidden”
  directory, /usr/games/hide, that may only be accessed
  by the dm program. dm
  determines if the requested game is available and, if so, runs it. The file
  /etc/dm.conf controls the conditions under which games
  may be run.
The file /etc/nogames may be used to
    “turn off” game playing. If the file exists, no game playing
    is allowed; the contents of the file will be displayed to any user
    requesting a game.
  - /etc/dm.conf
- configuration file
- /etc/nogames
- turns off game playing
- /usr/games/hide
- directory of ``real'' binaries
- /var/log/games.log
- game logging file
Thedm command appeared in
  4.3BSD-Tahoe.
Two issues result from dm running the games setgid
  “games”. First, all games that allow users to run
  UNIX commands should carefully set both the real and
  effective group ids immediately before executing those commands. Probably more
  important is that dm never be setgid anything but
  “games” so that compromising a game will result only in the
  user's ability to play games at will. Secondly, games which previously had no
  reason to run setgid and which accessed user files may have to be modified.