Spambots can easily be stopped instantly with one of two MODs. The RAC MOD or the Security Question MOD will add a new field to the registration page which the bots cannot deal with. You can mass delete any spambot accounts you have by using the Starfox Admin Toolkit.
More information is in the sticky topic Preventing Spam - Humans and Bots
at the top of the 2.0x Support Forum.
The Starfox Admin Toolkit can be download by clicking here