Huge wave of fake registrations. Advice needed

Hi StackIdeas,

Since RC1 test and now the stable release my social network experience a lot fake registrations, even with re-captcha activated.

Any tips how to prevent software/spam registrations? As well as tighten up the security.

One probability is "short registration" cause this problem.

Any way to disable "short registration" form?

Cheers
Kal