I just came across a handy tool for DreamHost users called ip-abuse-lookup.sh. This shell script analyzes error and access logs for a domain, looking for the IP addresses that have connected to your site the most often.

It checks for IP addresses that cause a Concurrent Connection Limit Exceeded error, which is a strong indication they are an automated bot of some kind. The script also scans for Internal Recursion Errors which can have very negatively effect your speed and server resources often caused by poorly configured .htaccess files.

After the script finishes scanning your logs, it will present you with the .htaccess code you can add to your site’s root .htaccess file to block the IP addresses the script found to be abusive.

For more info: DreamHost wiki page for ip-abuse-lookup.sh - with detailed instructions and full source code.