After multiple tries now to stop it I can't keep spam bots/advertisements away from posting in crap my forums. I have a verification image, verification questions, anti-spam mod and even email verification yet they are still somehow getting past. I'm using SMF and if anyone has any other tips or experience from keeping them away besides deleting/banning them It would really help because I'm stumped right now.

Well they might have registered before the verification was added so they're still registered better look for them in the users and delete / ban them

That's what I'm having as well. I'm coming to consideration of buying a forum system such as IBP or VB5... SMF would be very very very great if the bots didn't come.

In the mean while, make registrations admin approval.

Yes I was thinking of getting a vBulletin license but I'm strapped for cash right now coming up to Christmas. As for admin approval I could but it's not a permanent solution, If I start to get more traffic it's going to be hard to upkeep all the new members. I really want to know who has the time to get through all my security features and activate their account just to post some advertisement about shavers and handbags...

It gets me thinking though, are there any key words spam bots are attracted to or is it just site activity.

I wouldn't even say it's activity or key words. Every single time I have used SMF on any site, bots eventually get attracted to the site and register and post spam. It seems to be only SMF for me at least, though. I've had a few occurrences with myBB, but other than that using a paid forum software such as vBulletin, IPB, and xenForo, I've never had issues with that.

What questions are you using? I used to have a load of bots, though adding some difficult questions (nothing mathematical) and using recaptcha helped a lot.

I use reCaptcha, no differences imho.

I'm having a hard time keeping out spambots with IPB recently. Though, I haven't enabled their anti-spam service currently because my license's expired and I don't feel like paying $25 again. Currently, I have blocked China, Russia and Ukraine through htaccess in the root folder of my forum. This seems to help quite a lot. Also enabling Q&A challenge with "different" questions helps. Spambots can detect simple Q&A like 'What is 2 + 2'.

I did use basic maths questions but they bots tend to be able to figure them out automatically, I'm using specifically SA-MP related questions now but they still get through. I'm going to compile a list of all the locations they're coming from and block whichever country it is like you have.

From all the other replies I see that SMF might be the problem, thanks guys, I'll certainly consider VB or others in the near future

I have IPB boards too, and I originally had issues with spambots, however, I enabled e-mail verifications and complex security questions, mostly related to the community (you would need the SA:MP browser to know the answers). After that, I deleted the bots that were registered before the questions (questions, add many of them!) and their posts, and never had any issue with bots again. My forum has been clean for a long time.