Working good for me in 3.8, 60-80 legit regs a day with maybe 2-4 spammers getting through that I manually ban before they even post by watching registration emails as they come in.
Add a few extra questions to the registration and the bots stick out like a sore thumb...

This mod is helpful, but will not catch all spam bots. You need multiple layers of defense.
Look into stopforumspam, bad behavior, projecthoneypot and spam-o-matic.

Yes it works on my 3.8 and has stopped thousands upon thousands of bots and not interfered with even one human.

I haven't had this miss a bot yet. Not even one, out of many thousands of registration attempts. I got rid of most all other anti-spam measures.

HUMAN spammers.... Those are going to get through almost no matter what you do anyway but those are a extremely small percentage of the overall spam problem.

This Mod makes all the others superfluous. This one among them all should be part of native vBulletin.

Installed this today and it blocked two using the same email, the third one got through though.

thanks. not even launched yet and have dozens of these spam registrations. appreciate this mod.

is this working for vb 4?

In this thread there are instructions on making this Mod compatible with vB4.

There are instructions to make it work on VB4 a few pages back.

Spam increase lately =/

I'm sure this lightweight will help in some way, thanks