A parasitic meme embedded in a sig block. There was a meme plague or fad
for these on Usenet in late 1991. Most were equivalents of I am a
.sig virus. Please reproduce me in your .sig block.
. Of course,
the .sig virus's memetic hook is the giggle value of going along with the
gag; this, however, was a self-limiting phenomenon as more and more people
picked up on the idea. There were creative variants on it; some people
stuck ‘sig virus antibody’ texts in their sigs, and there was
at least one instance of a sig virus eater.