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RE: AT&T Blocking ICMP (was RE: AT&T US Network Slowdown?)

  • From: Mark Segal
  • Date: Tue Aug 19 13:46:29 2003

UPDATED: The Nachi worm will infect vulnerable Windows XP and 2000 machines 
using the same exploit used by the MS Blast worm family. The main difference
between Nachi and MS Blast, is that Nachi will remove and disable MS Blast
infections that it encounters, and download and install the correct MSRPC
DCOM patch from Microsoft. This action will permanently close the MSRPC
DCOM vulnerability.  The Nachi worm will not patch the WebDAV vulnerability
on Windows 2000 Servers.

Patches DCOM and removes MBLAST.. Why doesn't Microsoft release this, or did
they? :).


Mark Segal 
Director, Network Planning
FCI Broadband 
Tel: 905-284-4070 
Fax: 416-987-4701

Futureway Communications Inc. is now FCI Broadband

-----Original Message-----
From: Ingevaldson, Dan (ISS Atlanta) [] 
Sent: August 19, 2003 12:30 PM
To: Paul Jasa;
Subject: RE: AT&T Blocking ICMP (was RE: AT&T US Network Slowdown?)

The "Nachi" worm propagates via MSRPC DCOM and the IIS WebDAV bug.  It may
be causing this storm because it runs 300 scanning threads, and it pings
each IP first.

MS Blast wasn't multithreaded.

Daniel Ingevaldson
Engineering Manager, X-Force R&D 
Internet Security Systems, Inc.
The Power to Protect 

-----Original Message-----
From: Paul Jasa [] 
Sent: Tuesday, August 19, 2003 12:19 PM
Subject: AT&T Blocking ICMP (was RE: AT&T US Network Slowdown?)

A call to AT&T Worldnet confirms that AT&T Worldnet service is blocking ICMP
in order to deal with an undefined emergency.  Nothing posted on their site,
nor any other info is available.  If anyone has info related to this "icmp
outage", please advise.  Thanks! pj

Paul Jasa 
Network Engineer 

-----Original Message-----
From: Sean Crandall []
Sent: Tuesday, August 19, 2003 02:12 AM
To: Paul Jasa;
Subject: RE: AT&T US Network Slowdown?
Importance: High

> Dear Nanogers,
> Is anyone aware of a "slowdown" issue throughout the US AT&T network 
> since 8/18 at around 4pm which is causing a lot of internet circuits 
> (including DSL) to be inaccessible and/or appear down from the outside 
> world?  AT&T says this has been escalated to "Level 4" with no ETA and 
> affecting the whole country.  I am seeing this problem in the San 
> Francisco area.  Just wondering if anyone else is experiencing 
> anything that would confirm AT&T's claim, and fishing for more info 
> about the possible cause and ETA.  Thanks!

We are currently seeing the slowdown on our network in San Jose. Started
about exactly the time frame that you mentioned.  The rest of the country
(oddly) seems unaffected by this at the moment, but San Jose is getting
hammered by something.

Still trying to sort out exactly where it is coming from.


Sean P. Crandall
VP Engineering Operations
MegaPath Networks Inc.
Pleasanton, CA  94588
(925) 201-2530

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