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Date: Fri, 30 Jan 2004 00:26:51 -0800
From: Luigi Rizzo <rizzo@icir.org>
To: Pawel Malachowski <pawmal-posting@freebsd.lublin.pl>
Message-ID: <20040130002651.A90690@xorpc.icir.org>
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	11:49:47PM +0100
cc: freebsd-ipfw@freebsd.org
Subject: Re: 'prevmatch' patch
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On Thu, Jan 29, 2004 at 11:49:47PM +0100, Pawel Malachowski wrote:
> On Tue, Jan 27, 2004 at 01:02:24AM -0800, Luigi Rizzo wrote:
> 
> >  + add a new opcode that matches arbitrary bit patterns;
> 
> Only in packet headers or in packets data? (Blocking x-kazaa
> without the need of using Snort etc.;))

in the flags. It is completely trivial to implement a generic 'match'
opcode to look for specific payloads, but 1) it would be
very expensive to run on the packets, and 2) i do not see
much of a point, viruses will soon become somthing like

	useful instruction
	jmp 1f
	random junk
    1:	useful instruction
	useful instruction
	jmp 2f
	random junk
    2:	useful instruction
	...

thus defeating any virus scanner based on signatures.

cheers
luigi

> 
> -- 
> Pawel Malachowski
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