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Network Security Snort-Signatures
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Re: [Snort-sigs] DHCP Attack

Subject: Re: [Snort-sigs] DHCP Attack
Date: Thu, 19 Aug 2004 22:56:55 -0500
On Thu, 2004-08-19 at 14:30, Nick Hatch wrote:
Where do you have your Snort sensor for this rule? There are quite a few 
tools to find Rogue DHCP servers, but our problem has been finding a 
graceful solution to mitigate the amount of hardware needed to watch 30 
subnets.

How about setting up a script on a box whose segment is monitored by
Snort. That script can fire a dummy "whos-my-dhcp-server-daddy"
broadcast query packet to 255.255.255.255 port 67 and see what machines
respond (server:67 to client:68... iirc). That way you don't need to
monitor each collision domain, only your broadcast domains.

In essence, you're baiting the rogue DHCP server with fake DHCP queries
:)

Regards,
Frank

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