What country do they come from?
Mostly from Russia and China; some from Germany, France, and Sweden, then after that, just about anywhere.
The major offenders, as identified by their emails, are a Russian mail service called 'mail(dot)ru', followed by gmail. I find this odd, and a little offensive, since gmail is a service of Google, whose motto is, "Do no evil." And yet they seem unwilling to police their own product's use. Plus, they provide seemingly unlimited machine-generated (and likely disposable) email addresses, perfect for spamming.
This gets into a problem with international law, I'm sure. Read Terms of Service or End User License Agreement for any software, and you'll see that spam is prohibited. Big deal, sue us in international court, ha ha ha. I have noticed that we get almost NO spam originating in the USA. Court jurisdiction for that is in California for almost every TOS and EULA I've ever read.
Regarding the use of gibberish usernames, something I've noticed lately is that the Chinese have the most consistently perfect English-looking names in use. I often have to do a deeper check to make sure where a post is from, but I've gotten to calling it Chinese before I run it, and I'm usually right.
Some fools just don't care; I've seen -- this is a fact -- someone logged in here with the username, 'click here.'
The ones that mystify me are what I call 'squatters.' The board categorizes them as 'inactive users,' accounts with a zero post count. They just sign up and sit there forever (or until I kick 'em) and never post anything. Nearest I can guess, they must get a hit count reported back by crawlers and bots, giving them some kind of credit for just being somewhere.
Rick, you asked if assistance was needed . . . I don't think there's a need for another person to help with the spam -- Robert Moriyama and I handle the most of it -- but someone else once mentioned that there is an awful backlog of work in archiving old stories. I'm not sure I want to add 'board librarian' to my resume (and workload), but if you can figure out who to ask, there's some work that needs done.