I've never had any problems with spam before but when I checked my forum today I saw lots of spam threads. Some were in Russian though many were in English.
I checked some users and they had fully validated their account using Gmail. The spam is undoubtedly automated though.
Some users have signed up using the domain andasio.com.
At the moment I am getting a new thread every few minutes and the IP addresses are all different so there doesn't seem to be any way to stop it
(note: I haven't installed any new add ons or mods in a while so I don't think that's the issue)
I used to have this problem with vBulletin though this is the first time I've ever had a problem with XenForo. It's kind of taken me by surprise to be honest.
Any idea how this is happening and how I can stop it?