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RE: Comcast using IPS to protect the Internet f rom their home user clients?
From: Chmielarski TOM-ATC090 <Tom.Chmielarski () motorola com>
Date: Wed, 10 Mar 2004 07:46:09 -0600

Yes, they say they are now doing this.
-----Original Message-----
From: full-disclosure-admin () lists netsys com [mailto:full-disclosure-admin () lists netsys com] On Behalf Of Frank 
Sent: Monday, March 08, 2004 8:29 PM
To: full-disclosure () lists netsys com
Subject: [Full-disclosure] Comcast using IPS to protect the Internet from their home user clients?

This post should probably have gone to SF-PenTests, but since it is more of a discussion item, I thought about Full 
Disclosure, the list for vuln info and everything else :)

Anyhow, I noticed that certain vulnerability scans, for example scans using Nikto and similar tools, when run from a 
Comcast address show a different behavior than when they are run from a clear, uncontrolled Internet connection (i.e. 
corporate T-3). In fact, it appears like Comcast has an Inline-IDS (some call it an IPS ;) sitting on its wires, 
filtering out certain signatures and blocking subsequent access for a short period of time. For example, scan 
progresses, then hangs inexplicably, then resumes, trips a sig, and hangs again. At the same time, the same scan from a 
non-Comcast address continues without any hick-ups. Targets have been ruled out (up and running, verified at the same 
time from different addresses), and connectivity to the rest of the net remains. It's looks like just the src-dst 
address pair is used so that all connections from a Comcast src to that particular dst are blocked for a short moment 
(1-5 minutes).

Has anyone else noticed that? Is Comcast actually attempting to keep all those worms'n'viruses of their clients away 
from the Internet?

How many other ISP's are known to use IPS's inline to protect themselves from the 'Net, or protect the 'Net from 

Frank (routing all scans via VPN through corporate hosts ;)

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