[Dshield] ISS "Stumbler" advisory questions

Joe Stewart jstewart at lurhq.com
Fri Jun 20 14:08:22 GMT 2003

>From the X-Force "Stumbler" advisory:
> X-Force has been tracking reports of suspicious and widespread Internet
> traffic with a TCP Window size of 55808. A substantial amount of traffic
> captured from sites around the world point to a new distributed port
> scanning system.
... snip ...
> Each agent attempts to map IP addresses and open ports corresponding to 
> each IP address by sending a TCP SYN packet with a random destination port.

This doesn't appear to be the same pattern of activity seen since May. Many
people have reported activity from a single spoofed IP to a single destination 
IP from a random but non-varying source port to a random but non-varying 
destination port - for weeks at a time. I've seen this on several networks we
montor. I see no way this could even pretend to be an effective distributed

Intrusec seems to feel that the trojan they found is a copycat; someone
created a trojan to try and match the described behavior/traffic with winsize 
55808. Probably someone's idea of a joke on the infosec community. The files
ISS describe match the files Intrusec described, so why does ISS/X-Force feel 
that Stumbler is the true source of the traffic?


Joe Stewart, GCIH 
Senior Intrusion Analyst
LURHQ Corporation

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