RE: switched n/w

["David Gillett" <gillettdavid () fhda edu>]

  In the normal run of things, switched data would not be sniffable
without administrative access to a switch.  But there are techniques,
such as ARP poisoning, by which an attacker can intercept, and perhaps
even modify, switched traffic.
  In general, it is probably easier to change data on a host than in
transit, and ARP poisoning requires a host on the switched network to
perform the attack.  So my guess is that at least one host on your
network is compromised, OR at least one of your users is up to something.

  I alluded above to administrative access.  Most modern switches include
a provision for a special port configuration to allow traffic to be sniffed.
I would do that, paying particular attention to the ARP traffic.

David Gillett


> -----Original Message-----
> From: kaushal [mailto:kaushal () rocsys com]
> Sent: Tuesday, December 07, 2004 10:30 AM
> To: security-basics () securityfocus com
> Subject: switched n/w
>
>
> Hi,
>    Iam a bit new to network securities.We have a switched
> network and to
> my knowledge a hosts' data cannot be sniffed by other host by runnning
> tcpdump.But Iam receiving complaints from few users that their data is
> being changed/manipulated.Is this possible?
> How can I avoid this at the host level?Does this mean the server has
> been compromised?Any help or pointer in this aspect would be highly
> appreciated.
>
> thanks in advance.
>
> kaushal.