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Is there any tool on Linux to automatically modify iptables so as to block a troublesome client based on an analysis of the Apache log? I help run a site that sometimes get overwhelmed by requests from a particular user. The only solution is to add an entry in iptables to block the offending client. Its usually too late by the time I can react manually - hence, I would like some rule based mechanism to modify the iptables. I would guess that some kind of fuzzly logic or statistical analysis would be necessary.

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up vote 10 down vote accepted

You can use something like fail2ban, which IIRC, has an Apache log checker built in.

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fail2ban comes very close to doing what I want. Looks like I'll have to dig through the source a bit. – Rangachari Anand Apr 30 '09 at 18:51

You might want to consider using iptables to rate-limit incoming connections. Which in its most basic setting will give you the ability to limit incoming connections to a number per minute.

For example, you might want to only allow 10 pings per minute from a single IP address. It does get a little more sophisticated than that, with the option to set burst limits on top of long term average limits.

Some good instructions on setting it up

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Excellent - I had no idea that iptables could even do that. This could be very useful. – Rangachari Anand Apr 30 '09 at 18:50
I'll dig out an excellent guide i read recently on it – Guy C Apr 30 '09 at 18:50

Check out OSSEC. Best log file analyzer I've used. It also supports active response based on analysis.

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