Any way to automatically prevent IP addresses from continually attempting to create account

Hey,

Does any one know of an automated system(plugin?) that if an IP tries to create an account and fails (after say 3 times) it blocks that IP from accessing the site for say ~48 hrs?

I have had many, many different IP's constantly try to register for an account but they can't get past the captcha & anti-spam database - however they continually for days on end constantly try to register (I guess it must be some kind of bot?)  It's so frequent that my hosting service keeps wanting me to upgrade my account due the server overhead.

Something that would at least reduce their attacks to 3x per 48 hours would be wonderful - if it exists.


Any ideas?

 

Thanks