Nachi Worm apparently causes "Live Lock" on 4.7 server

paul pkdb1 at
Thu Aug 28 21:23:58 PDT 2003

James C. Durham wrote:

> It turned out that we had several Windows boxes in the building that had been 
> infected with the Nachi worm. This causes some kind of DOS or ping probe out 
> onto the internet and the local LAN.
> Removing the inside interface's ethernet cable caused the ping times on the 
> outside interface to go back to the normal .4 milliseconds to the router.
> Apparently, the blast of packets coming from the infected boxes managed to 
> cause a "live lock" condition in the server. I assume it was interrupt bound 
> servicing the inside interface. The packets were ICMP requests to various 
> addresses.

I could be way off here, but is there any way to isolate machines 
that send a sudden blast of packets, either by destination address 
(make a firewall rule that drops those packets) or working out 
their MAC addresses and dropping their connectivity? Or scan for 
open ports and block unsecured systems from connecting?
> My questions is.. what, if any, is a technique for preventing this condition? 
> I know, fix the windows boxes, but  I can't continually check the status of 
> the virus software and patch level of the Windows boxes. There are 250 plus 
> of them and one of me. Users won't install upgrades even when warned this 
> worm thing was coming. But, i'd like to prevent loss of service when one of 
> Bill's boxes goes nuts!

Where I work, at the University of Washington, the network staff 
were dropping as many as 200 machines *per day* off the network. 
If a machine was found to have an open RPC port (we run an open 
network), that was enough to get your network access cut off.

I realize these are political solutions more than technical ones, 
but they may be of some use.
Paul Beard
whois -h ha=pb202

Satellite Safety Tip #14:
	If you see a bright streak in the sky coming at you, duck.

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