RE: VALN hopping

["Joshua Berry" <JBerry () PENSON COM>]

VLAN's can certainly be bypassed as long as they are not setup properly.
@stake did a security review of VLAN's which can be found here:
http://www.cisco.com/warp/public/cc/pd/si/casi/ca6000/tech/stake_wp.pdf

And cisco has their own documentation on it here:
http://www.cisco.com/warp/public/cc/pd/si/casi/ca6000/prodlit/vlnwp_wp.p
df

These outline potential problems and their solutions.  I would be a
little skeptical if it was only Cisco doing the research into VLAN
exploitation but I am a little more comfortable since @stake did
research into it as well. 

-----Original Message-----
From: Steve McLaughlin [mailto:Steve.McLaughlin () aggreko co uk] 
Sent: Wednesday, October 05, 2005 6:28 AM
To: David Barroso; Hayes, Ian
Cc: security-basics () securityfocus com
Subject: RE: VALN hopping

According to Cisco they are a good security measure.
I don't know of any exploits which enable you to VLAN hop.

Does anyone know of any?

On a layer 2 switch the ports are physically assigned to a VLAN, and
therefore require a Layer 3 device to route traffic between them.

On a layer 3 switch this might be different because of it's layer 3
capabilities built into the appliance. Though, I still don't know of any
way of 'VLAN Hopping', although I could be wrong.

And if this is possible on a layer 2 switch then please explain?

Steve McLaughlin - Security Analyst
(CCNP, MCSE:Security, Security+)

-----Original Message-----
From: David Barroso [mailto:dbarroso () s21sec com]
Sent: 30 September 2005 18:54
To: Hayes, Ian
Cc: security-basics () securityfocus com
Subject: Re: VALN hopping

> WWe are having a heated discussion about using VLAN's as a type of
> DMZ, so
> > I am asking the experts.  I prsonally like to see physical
isolation;
> > however, our network person doesn't feel there is a threat of VLAN 
> > hopping.  Please let me know your opinions.

If they are new devices with up-to-date OS versions it is not very
likely that attacks similar to double encapsulated 802.1q packets will
succeed.
On
the other hand, if they are not properly configured and/or hardened,
other attacks can be accomplished, like for instance, with Cisco
devices, setting up a trunking if DTP settings are poorly configured
(see http://yersinia.sourceforge.net for performing that attack).

--
David Barroso Berrueta
Not one day goes by that I don't ride, 'til the infinite, the horse of
my imagination

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