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.
[glossary]