New Vegas's "Contain the Virus" quest or how was it called, in the BoS bunker.
This wasn't a serious virus, it was made by a prankster (the scientist tell something like that and see the messages that it writes when you "catch" it). Nowadays malware is 99% of the time serious (and often unnoticed) but viruses in old computers were mainly pranks (e.g. the Stoned virus that modified your boot drive to say "Your pc is now stoned!") - though some would destroy data while being trollish about it (i remember my father's computer having a variation of the - otherwise harmless - ping-pong virus that was deleting a random FAT file entry every time the ball bounced on the screen).
Considering the game's themes (and the messages it displays) i think they modeled the "virus" after these prankster viruses and not serious ones.
Even worse, if you have a high enough computer skill (at least I think it is computer skill), you can tell the person responsible for giving you the quest the "obvious" solution. He then says something like "You are right, how did I not think of that?", but for some reason that does not bring about the conclusion of the quest but instead you are supposed to do it the idiotic way anyway.
You need to find the two instances of the virus in the terminals and those instances jump between terminals every cycle. The difference with the high skill option is that if you find an instance it gets "locked" to that terminal so even if you fail and the cycle restarts, the instance remains on that terminal (without the skill both instances jump to a random terminal).
I just looked into this and apparently it was inspired by a real virus from 1971 called
Creeper that was moving between ARPANET computers. Funny enough another worm was also made (called Reaper) that was deleting Creeper instances :-P.