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RE: Caching a sniffer
From: "Andrew Shore" <andrew.shore () holistecs com>
Date: Thu, 25 Mar 2004 16:30:05 -0000

Agreed, however, any activity that tricks a switch port into "opening
up" usually requires someone to flood massive amount of traffic into the
switch, this should alert any network manager to some kind of wrong
doing plus in a large organisation all switches should be logging error
event to some form of management server.   

Andrew Shore
Senior Security Specialist
DDI. 01302 308 165
andrew.shore () holistecs com
Company Number 04943010
VAT Number 828 8635 82
Holistic Technologies Ltd
Unit 7 Shaw Wood Business Park
Shaw Wood Way
South Yorkshire
T. 0870 240 1442
F. 0870 240 1443

-----Original Message-----
From: David Gillett [mailto:gillettdavid () fhda edu] 
Sent: 25 March 2004 16:21
To: Andrew Shore
Cc: security-basics () securityfocus com
Subject: RE: Caching a sniffer

A switch is not a hub/router. In fact it is a micro segmented bridge.

A switch operates at layer 2 of the OSI model ie MAC address layer. 

  Amen, brother.
Therefore if someone has plugged a scanner into a network point they
will not be able to sniff any useful information from the network 
unless that person has admin access to the switch. You can check 
this by ensuring that none of the ports on the switches are in span 

  While you need admin access to set up a span port, Shawn and I have
alluded to two different techniques which can allow non-admin users
to sniff traffic on a switched network.  It's true that neither of these
is quite "normal behaviour" -- they involve using special tools to
modify the behaviour of hosts or switches.  But the tools exist and
are readily available, and so the issue that confronts admins is how
to detect and/or frustrate their use.

David Gillett

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