A Joe Job is essentially
spam designed to look like it's coming from someone else.
In
1996, the website
Joe's cyberpost (
joes.com) -- a hosting company -- had a user who
spammed newsgroups advertising his page. His account was killed for a breach of joes.com's
AUP.
Our spammer then went on to send millions of spams; but this time he forged the return address to make it look like Joe Doll, the owner of joes.com, was doing the spamming.
Well, joes.com was inundated with complaints from newsgroup users and email account holders. They were also DOS-attacked by a bunch of angry haxors too lazy to properly check the source of the spam. Joes.com's server died on or about New Year's Day, 1997.
Since then, the term Joe Job has referred to anyone trying to pull the same trick.
A Joe Job is essentially malicious. A spam with dave@hotmail.com in the from: line isn't a Joe Job, unless the spammer was trying to pin the blame on Dave. So while forged from: lines are almost standard-issue on modern spam, Joe Jobs are still pretty rare.
Of course, the anti-spam community has learnt a few tricks since 1997, and so have the spammers. Modern Joe Jobs involve forged email headers and other nasty tricks to make it really convincing. And with the advent of dnsBLs like SPEWS and peoples' personal plonk lists, a successful Joe Job can really hurt the victim.
(This writeup now cited in the official Jargon File definition, and in a US patent application!)