RE: VALN hopping

From: Joshua Berry (JBerry_at_PENSON.COM)
Date: 10/05/05

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    Date: Wed, 5 Oct 2005 13:03:41 -0500
To: "Steve McLaughlin" <Steve.McLaughlin@aggreko.co.uk>, "David Barroso" <dbarroso@s21sec.com>, "Hayes, Ian" <Ian.Hayes@wynnlasvegas.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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