Three Strikes and You're Out!
Closes comments across the board to IP addresses that are behaving badly. Here's one that should be in every admin's toolkit..
Three Strikes and You’re Out temporarily closes comments on your blog across the board to anyone who is coming from an IP address that is repeatedly behaving badly. It examines your Bad Behavior logs and spam queue and its own internal log, and if your visitor has notched up three or more bad hits, it responds by closing comments right across the board on your blog.
Installation is straightforward: download it, unzip it, copy the file three-strikes.php into your /wp-content/plugins directory, and enable it in your dashboard.
By default, it will close comments after the offending IP address has tried something naughty three or more times in the past seven days. You can change these defaults by editing the define() statements at the top of the plugin’s source code
Here's the link:
http://jamesmckay.net/code/three-strikes/