Prevent another user from dittoing your machine (QNX)
noditto [-g groupno]... [-u userno]...
The noditto utility is used to prevent other users from viewing or controlling your console screens using ditto. By default it disallows all ditto attempts (except those by root, who is immune from noditto). Users and members of groups may be selectively allowed by specifying one or more -g or -u options.
The attempts (both successful and unsuccessful) to ditto your machine may be logged by noditto by specifying the -v or -l options. The -v option simply logs attempts to /dev/tty (the console it was started from, regardless of whether the standard output has been redirected), while -l writes the log information to the specified filename.
The noditto utility forks a copy of itself in the background, then exits. The forked copy arbitrates whether ditto has permission to ditto the machine. To re-allow dittoing for all users, use slay noditto.
Prevent all users (except root, who is exempt) from dittoing your machine:
noditto
Allow only users in group techies to ditto your machine:
noditto -g techies
Allow only users john and carol to ditto your machine:
noditto -u john -u carol
Disallow all users but group techies from dittoing your machine, and log all ditto activity (including unsuccessful attempts) to /home/fred/dittolog:
noditto -g techies -l /home/fred/dittolog