This is a bit of history for me; perhaps someone who has actually seen it can chime in.
There were a number of Star Trek themed computer war games with basically the same concept: fly the Enterprise around blowing up Klingons and other enemies of the Federation. If I understand correctly, xtrek was somewhat different — a multiplayer space combat game set in Star Trek with factions from that setting and using X11 for display, thus the "x" in the name. I believe that Xpilot is a similar game that should be less obscure.
Administrators, of course, sometimes considered such things wastes of "valuable computing resources" and did what would be expected, leading to a cat-and-mouse metagame of playing the game without getting caught by the system operators. :-)