I am running a series of web servers and already have a pretty good set of firewall rules set up, however I'm looking for something to monitor the traffic and add rules as needed. I have denyhosts monitoring for bad SSH logins, and that's great - but I'd love something I could apply to the whole machine that would help prevent bute force attacks against my web applications as well, and add rules to block IPs that display evidence of common attacks.

I've seen APF, but it looks as though it hasn't been updated in several years. Is it still in use and would it be good for this? Also, what other solutions are out there that would manipulate iptables to behave in some adaptive fashion?

I'm running Ubuntu Linux, if that helps.