PassHack Killer
This script, when properly installed, will log and track any failed authentication attempts for your members area(s). When the failed number of attempts coming from one certain IP exceeds a limit you set, the script will automatically block that IP from accessing your entire site. This will also effectively block any person trying to brute-force their way into your members area(s). Whenever a block is placed, you will be notified by e-mail so you can take the appropriate action, e.g. contact the offenders ISP. The blocking system is totally automated, provided you have set up the correct .htaccess entries.