Firewalls: Re: icmp considered dangerous ?

Firewalls
(October 1992)

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Subject:	Re: icmp considered dangerous ?
From:	jim @ tadpole . com (Jim Thompson)
Date:	Thu, 29 Oct 92 07:16:24 CST
To:	Firewalls @ GreatCircle . COM, chytil @ eunet . co . at

It (icmp, via ICMP_ECHO (request)  and ICMP_ECHOREPLY) 
could be used to 'probe' your network.

A 'badguy' seding lots of SOURCEQUENCH packets could provoke
denial of service conditions.

To say nothing of the number of Sun machines that still crash
given any packet with options in it, or covert channels that could
be constructed out of icmp messages.

Jim

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