Hello,

On Thursday 16 May 2002 06:06, Mike Karras wrote:
> Does anyone know how to filter packets based on data in a certain offset
> in a TCP packet?

You can use filtering application proxy (ie zorp or squid or whatever).

> I'm trying to filter data to certain URLs behind a firewall..
> Say that I'm getting flooded with HTTP POST requests for a URL:
> http://www.someplace.com/index.html?somevar=blah&something=else
> in such magnitude that I'm getting DOS'ed.
> By the time that it gets to the firewall, all domain information is gone,
> true?
> So I would have to test against that URL.
> I haven't found any way to do this so far.

Because a packet filter is not supposed to do that. As its names
says it's a packet filter, not a filtering application proxy.
This answer is going to go into the FAQ very soon.
http://www.netfilter.org/documentation/HOWTO//netfilter-extensions-HOWTO-3.html#ss3.16
http://freshmeat.net/projects/zorp/?topic_id=43%2C44%2C151
http://freshmeat.net/search/?q=squid&section=projects

Have a nice day,

Fabrice.
--
Fabrice MARIE
Senior R&D Engineer
Celestix Networks
http://www.celestix.com/

"Silly hacker, root is for administrators" 
       -Unknown

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