What do these spammers believe that they will achieve? Seriously?
A lot of "spammers" are in reality just hacker exploits and bots used on boards to ruin/takeover the board.
You look at my board here:
http://www.chimera-art.com/bbs/index.php
You'll see I fell pray to one of these exploits on my board a long time ago. 80 some thousand registered users, all because of an exploit.
Haven't had time to fix it. Meanwhile my database continues to grow everyday. Eventually it'll become a big problem. It shut down my board once already.
More than likely that's what this is. It's important that the board admin keeps the board up to date, patched, and notifies the software creator of this type of thing.