Although not a virus, the command shutdown (Windows or *nix) will shutdown a computer.

For Windows, the usage is shutdown [-i | -l | -s | -r | -a] [-f] [-m \\computername] [-t xx] [-c "comment"] [-d up:xx:yy] with the usage: -i Display GUI interface, must be the first option -l Log off (cannot be used with -m option) -s Shutdown the computer -r Shutdown and restart the computer -a Abort a system shutdown -m \\computername Remote computer to shutdown/restart/abort -t xx Set timeout for shutdown to xx seconds -c "comment" Shutdown comment (maximum of 127 characters) -f Forces running applications to close without warning -d [u] [p]:xx:yy The reason code for the shutdown u is the user code p is a planned shutdown code xx is the major reason code (positive integer less than 256) yy is the minor reason code (positive integer less than 65536)

In *nix, the following applies:

shutdown [-a][-t sec][-krhnfFc][time][warning-message] -a Use /etc/shutdown.allow. -t sec Tell init to wait sec seconds between sending processes the warning and the kill signal, before changing to another runlevel. -k Don't really shutdown; only send the warning messages to everybody. -r Reboot after shutdown. -h Halt after shutdown. -n Don't call init to do the shutdown but do it ourselves. The use of this option is discouraged, and its results are not always what you'd expect. -f Skip fsck on reboot. -F Force fsck on reboot. -c Cancel an already running shutdown. With this option it is of course not possible to give the time argument, but you can enter an explanatory message on the command line that will be sent to all users. time When to shutdown. warning-message Message to send to all users.