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Date:      Mon, 9 Sep 2002 12:38:13 -0500
From:      "Kim Scarborough" <sluggo@unknown.nu>
To:        <freebsd-questions@freebsd.org>
Subject:   Content-based web filtering?
Message-ID:  <029901c25827$ac4977e0$23638780@uchicago.edu>

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I'm running an Apache web server on 4.6.2-RELEASE that hosts several virtual
domains. One of these is somewhat controversial, and every few days I've been
getting a distributed denial of service attack through massive numbers of
requests for a particular file from poorly-configured proxy servers all over
the world. It doesn't affect the OS, but it does choke httpd by using up all
the available servers.

In the past, I've blocked the DOS attacks by simply IPFW-ing out the offending
host, but with this attack there are hundreds of hosts. What is constant,
however, are the user agent and file request strings; they are always the
same. So if there was some way to filter based on that, I'd be safe (at least
for now). But IPFW can't do that, right? So I'd need to either find a firewall
that will, or maybe put a small proxy server to intercept these requests and
let everything else through to Apache.

Does anybody have any thoughts on how to deal with this? If you think one of
the two solutions above is the way to go, any software recommendations? Does
anyone have another idea altogether? I'm kinda stumped here, and the way I'm
dealing with it at the moment is to shut down the targeted site, which of
course is unacceptable.

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Kim Scarborough                                  http://www.unknown.nu/kim/
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"Football combines the two worst features of American life: violence and
committee meetings."
                                                               -George Will
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Now listening to: Raymond Scott - "The Happy Whistler"
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