ANSWER:

Hello and sorry for upping an old thread.
But this still might be interesting for TS and other people.

We have just launched new product – RdpGuard ( http://rdpguard.com )
it allows you to protect RDP from brute-force attacks.

It monitors Windows Security Event Log and if the number of failed login attempts from a single IP address reaches a set limit (three by default), the attacker’s IP address will be blocked on the firewall for 24 hours, then unblocked automatically.

I have to mention, this is not free product.

by S3 Browser Team from http://serverfault.com/questions/382351