Is there a free security log analyzer for apache?

Is there a free security log analyzer for apache?

What I need is a forensic log analyzer tool for apache to do the after math of a successful abuse of service attack which took place 2-3 month in the past. We are running a shared hosting service and one of our customers seems to have (or had) an exploitable script running. I suspect that I could find clues and hints in the logs but they are just too huge to browse through them manually or grep regexps from them.