[Snort-users] Suspicious ICMP traces
ryan at ...35...
Tue Oct 23 08:31:06 EDT 2001
On Tue, 23 Oct 2001, Demetri Mouratis wrote:
> I'm not really sure so I thought I'd pass this along for second opinions.
> One thing that raised my suspicions was that the ICMP packet seems to
> contain a UDP datagram within it. (Or am I jumping the gun on that?)
ICMP unreachable messages contain a portion of the original packet, so
that the hosts can determine which packet was rejected.
> So, here is the relevant portion of alert:
> [**] [1:485:1] ICMP Destination Unreachable (Communication
> Administratively Prohibited) [**]
> 10/21-20:21:24.622037 126.96.36.199 -> 192.168.75.7
Are you 188.8.131.52? Is 192.168.75.7 the real attacker address, or have
you sanitized it? That's a RFC1918 address.
> I've got maybe 10,000 of these over a few day period. I'm also seeing
> portscans from 192.168.75.7 so I'm pretty sure something is not right
Well, if you're sending ICMP unreachables in response to being
protscanned, that's pretty much what is supposed to happen.
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