Ahh, this is a distinction that I had to clarify here just last week. Just
because a switch is considered "hardware" and looks like a hub does not mean
that the configuration is hardware-based. To the contrary, it's
software...software that keeps track of which ports should be speaking with
which other ports. Getting one VLAN to bleed into another is not quite as
simple as just getting the switch to fail open and span all ports by
blasting a bazillion MAC addresses onto the wire, but it is well worth
remembering that we are talking about software when it really comes down to
it. Furthermore, if you have a manageable switch, which most of them are,
you can directly speak with the software there. SNMP, anyone? :)

----- Original Message -----
From: <Eduardo_CamposCREDOMATIC.COM>
To: <PEN-TESTSECURITYFOCUS.COM>
Sent: Tuesday, February 06, 2001 3:57 PM
Subject: Re: [PEN-TEST] Spoofing switched networks

Right, since VLANs are defined on hardware, how can you convince the switch
to give you a trunk port ?
That would be the only way to receive and send traffic to other VLANS.
VLANS were not designed with security on mind. Broadcast domain division in
fact is the best advantage you achieve with VLANs. Although, making VLANs
and creating access-lists on the router which enable communications between
them (if you permit it) can give you a very good way to have more strict
security.

                    "Lindqvist, Johan"
                    <johan.lindqvistDRIFTBO To:
PEN-TESTSECURITYFOCUS.COM
                    LAGET.COM> cc:
                    Sent by: Penetration Subject: Re:
[PEN-TEST] Spoofing switched networks
                    Testers
                    <PEN-TESTSECURITYFOCUS.
                    COM>

                    06-02-01 10:48 AM
                    Please respond to
                    Penetration Testers

Hi.

> Actually, sniffing isnt' that heard either. There are
> several ways to do
> it such as making the switch you are a trunk port and you need all the
> traffic. In order words, don't put a switch and VLANs in
> place and expect
> that to be your security because they can be defeated.

As for switching, I'm fully aware that it's not a security mechanism that
cannot be defeated easily. However that VLANs have no security impact is
news to me. Since VLANS are defined on physical switch port basis, how
could
they be used to receive or send traffic on other VLANs?

/Johan

--
Johan Lindqvist
Security Specialist
DRIFTBOLAGET AB, MÖLNDALSVÄGEN 81, 412 63 GÖTEBORG, SWEDEN
PHONE: +46 8-23 92 00 FAX: +46 709-73 46 70
DIRECT: +46 31-760 43 07 MOBILE: +46 709-73 87 07
johan.lindqvistdriftbolaget.com http://www.driftbolaget.com

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