From The Jargon File (version 4.4.7, 29 Dec 2003):
snark
n.
[Lewis Carroll, via the Michigan Terminal System]
1. A system failure. When a user's process bombed, the operator would get
the message “Help, Help, Snark in MTS!”
2. More generally, any kind of unexplained or threatening event on a
computer (especially if it might be a boojum). Often used to refer to an
event or a log file entry that might indicate an attempted security
violation.
3. UUCP name of snark.thyrsus.com, home site of the Jargon File versions
from 2.*.* on (i.e., this lexicon).