we are having problems with bots as well, they are constantly joining, the anti spam plug in watch dog does not work, we are using it at present and and are deleting more bots now than we did before we starting using it,

they are spiking our cpu and vm to the max according to our server, could you tell us if you are having spikes in yours as well as this will help us rule this out

I played with antispam to no avail and actually caused more problems for valid users than the spammers.

I added a custom question in the signup and made it required. Works a treat no more spam.

Whats your age (anti spam)?

Are you a horse (anti spam)?

How many fingers do you have (anti spam)?

One question like the above will solve your problems as long as its required and part of sign up.

Just add to Admin/users/Profile Questions How did you hear about us to the sign up page and give about 3 choices ie, internet search,website,friend, and make it required on sign up ,this will also stop the bots,i have never had any bots since i added this . 

you're right,,, at least (the changeble of antispammer profile question)  can be overcome spammers for a while....
and the combination of the Watchdog and antispammer (working together) can further reduce spammers..
GTranslated....

paul, i look at your site, your spammers the ones where the man has no face, sunglasses and hat, we are plagued with them, we use user approve so they never do anything as they jut get deleted never approved, we notice they cause masive spikes in cpu and vm even with your plug in they are coming through more than ever, we need a way to stop them landing on the site in the first place

Your last update antispammer is very good....more complete
From me +10 of available Free AntiSpammer
GTranslate

Dun read the thread, but what I did to end up the bots was:

- Put one more question in "Join Page" and set it as Require

- Don't put the join page as Welcome page, or best, create another page, without any link with Join page and make it the Guess' index

Since that I never get a 'blank avatar' bot (the massive one) anymore and I did it in Octuber~November.

Quote from Paul Cuffe Cit27

I am planning a update where a site owner makes say 10 questions then anti spammer will rotate the question every few days. to help protect from spam too

will waiting this feature