Just a little further info: Since September 22 we've had up to 20 new member submissions a day, many from Russian IPs and email addresses. No clue why, maybe our spam filter stopped working.
Anyway, to combat this we've turned off new users so only Admins can approve new members. We're working on a question and answer validation where new members need to answer a simple SEGA question. This should help. If you see any more spam, it is likely from accounts that were approved before the 22nd and hadn't posted yet. I'll ban and delete them as they appear.