How do I fix this?

[twincamfxd]

One of the boards I work on has been relentlessly beaten up with spammers. People registering just to make 1 post with 20+ links on it with everything from viagra to prescription meds for sale. It has gotten so bad we have closed registration, and we cant figure out where it is coming from. Any ideas on how I can stop this?

[peterska2]

Make sure you have email verification and image verification turned on as this will cut them down a lot. (vBOptions > User Registration Options)

Also check if guests can post on your forum.

Finally, see what domains the registrations are coming from and consider banning registrations from those domains.