How to prevent spam regestration ?

[CloudyBright]

Is your forum seeking users from the entire world- like China, India and Pakistan?
You can see the ip addresses of the spammers and block them using MyBB
The two big spammers on my forum were from China and have been blocked by using 218.*.*.* and 36.*.*.* blockers.

Learn the ip address that are spamming you.
Then block those ip addresses.
That may work for you.

[NomanProdhan]

Thanks to you all for your suggestion.

I install the reg time plugin, change some reg question and set reCapthca . Currently I don't get any spam registration on my forum.
Thanks again to all for your suggestions (a)

[VoIP]

Goodluck! You will be golden with that.

[NomanProdhan]

Goodluck! You will be golden with that.

Thanks!!!!!

[effone]

Just a note:
Checkbox Validation plugin worths a try.