I just ran across this little security-related utility today. I don't know if it's available for Windows, but it's an awesome little tool for *nix servers.
What it does is read the access logs, real time, for any service it is configured to protect, i.e., ftp server, web server, ssh, etc... and immediately bans IP addresses based upon failed logins. It puts an immediate halt to things such as dictionary attacks.
It is simple to configure, extremely easy to install and set up, and at the same time highly configurable. It will work with both standalone daemons and services made available through inetd or xinetd.
Here is a link to their home page.
http://www.fail2ban.org/wiki/index.php/Main_Page