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Re: Pattern matching odd HTTP request
From: "Karsten W. Rohrbach" <karsten () rohrbach de>
Date: Wed, 19 Sep 2001 01:51:30 +0200

Bill McGonigle(mcgonigle () medicalmedia com)@2001.09.18 18:58:42 +0000:

On Tuesday, September 18, 2001, at 06:30 PM, Jake Khuon wrote:

You start to suspect a DDOS port-flood attack.  It's certainly causing 
me to
spawn a lot of httpds and occupying a lot of ports.
[...]
On Apache 1.3, this brings the number of httpd processes up to 
MaxClients, then each one waits 300 seconds (the default timeout) for 
the connections to time out, at which point the other connections are 
made, and the cycle continues.  A DDOS of this nature would be 
particularly nasty.  One client (happened to be on localhost) tied up 
the server for 6 minutes this way with the default Apache config.

indeed, that's nasty.
the quick fix action would be setting
    Timeout 5
in the httpd.conf, but this won't really fix the problem and make the
objects inaccessible for users with high latency links.

source ip based connection rate limiting would perhaps solve the
problem. are there any modules available out there to accomplish this
task?


Here's what the logfile for these attempts looks like:

127.0.0.1 - - [18/Sep/2001:18:43:06 -0400] "-" 408 -

Doh!

yup, i see them from time to time in some of my servers' logs, but not
at that rate jake reported. i cc'ed brian from the apache project,
perhaps they got some solution for this...

/k

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