In this new post to his site Kevin Boyd introduces a tool that you can use to scan your logs for login abuse, Fail2ban, and how to use it with your application's login attempts to ban IPs as needed.
Fail2Ban is a Python-based utility that hooks directly into the system's firewall to ban malicious IP addresses, and I'm going to show a few easy steps to make your site safer by blacklisting brute-force attackers. If you maintain a web application that doesn't have built-in authentication throttling, this might be the how-to you're looking for - alternatively, this would work as an additional way to punish pesky rogue connections.
His example uses the Fail2Ban ability to read files on the local system, as written by PHP and containing the failure message and an IP address, and adds IP blocks accordingly. He includes some sample code for the format you'll need to follow and a bit about setup and configuration of the Fail2ban tool.