From the jargon file:

B1FF /bif/ UseNet (alt. `BIFF') n.

The most famous pseudo, and the prototypical newbie. Articles from B1FF feature all uppercase letters sprinkled liberally with bangs, typos, `cute' misspellings (EVRY BUDY LUVS GOOD OLD BIFF CUZ HE"S A K00L DOOD AN HE RITES REEL AWESUM THINGZ IN CAPITULL LETTRS LIKE THIS!!!), use (and often misuse) of fragments of talk mode abbreviations, a long sig block (sometimes even a doubled sig), and unbounded naivete. B1FF posts articles using his elder brother's VIC-20. B1FF's location is a mystery, as his articles appear to come from a variety of sites.

However, BITNET seems to be the most frequent origin. The theory that B1FF is a denizen of BITNET is supported by B1FF's (unfortunately invalid) electronic mail address: B1FF@BIT.NET.

[1993: Now It Can Be Told! My spies inform me that B1FF was originally created by [Joe Talmadge, also the author of the infamous and much-plagiarized "Flamer's Bible". The BIFF filter he wrote was later passed to Richard Sexton, who posted BIFFisms much more widely. Versions have since been posted for the amusement of the net at large. See also Jeff K. --ESR]

See also JeffK@Somethingawful and do not confuse JEFFK with Jeffrey Komori