I got asked that recently when I couldn't remember my password.

Hoist by one's own petard!

Charlie, if the spammers are coming from the same IP range you can just add that to the block list in the site options.

You need to be careful how far up the IP chain you go, though - for a while (and I'm sure anyone who was around 5 years ago can work out why) I inadvertently blocked Australia!