RE: Re: Vlan's as effective security measures?

[<hugh_fraser () dofasco ca>]

> -----Original Message-----
> From: Brian Ford [mailto:brford () cisco com] 
> Sent: Friday, February 13, 2004 1:44 PM
> To: Fraser Hugh
> Cc: firewall-wizards () honor icsalabs com; jhall () ptavvs net; 
> LWare () e-one com
> Subject: RE: Re: [fw-wiz] Vlan's as effective security measures?
>
>
> Hugh,
>
> Please see my comments in line:
>
> At 11:58 AM 2/13/2004 -0500, hugh_fraser () dofasco ca wrote:
> > Regardless of the VLAN technology chosen, the basic reason for 
> > investing in this kind of technology is to manage bandwidth 
> and isolate 
> > traffic, not provide security.
>
> I don't agree with your wording here.  You seem to be 
> implying that VLANs 
> can not be made secure at all.  In fact, VLAN technology can be 
> secured.  Whether or not the level of security achieved in a 
> particular 
> design provides acceptable risk is design issue that is 
> reviewed all the time.


I'm referring to the reasons people usually invest in VLAN technology,
and that usually drives their deployment strategies and the way the
network's managed. I'm not referring to what the vendors priorities are.
I mentioned later in my note that newer technologies (like 802.1x) offer
the ability to do port authentication, but that's not been the driving
force in the past, and I'm certain isn't the reason for most existing
installations. I can address a lot of security issues by simply managing
my systems better, enforcing stronger authentication, encrypted traffic,
mandatory access controls,  etc.. But some systems don't support these
features, run legacy or purchased apps I can't change, or are simply
driven by business requirements that we, as a supplier, are forced to
accept.

I've been waiting for quite some time for even rudimentary IDS functions
in switches to address the problems I have deploying IDS sensors
internally. The response has always been that it would be nice and is
being looked at, but the fundamental design goal, and the metric by
which the product is measured, is switching speed. IDS functionality
consumes valuable horsepower.

Practically speaking, VLANs are usually used to control traffic, and are
managed by people responsible for providing this service. Security is
another issue, usually handled by a different set of people, with an
entirely different mandate.

Security's a tough enough feature to sell in pure security circles. In a
market where the major concern is providing enough bandwidth to support
the next big app (ie. Voip, video conferencing, etc.), it's not the top
priority.


> >  As such, the vendors haven't invested a lot in
> > security.
>
> That's a blanket statement that based on my own experience 
> with my employer 
> I would disagree with.

True enough, from the vendors perspective. I don't think the importance
of this has been made a high-enough priority to the customer though.
While security education is definitely one of my responsibilities,
security is still considered by many to be an expense that adds little
value to a company's bottom line, compared with a pipe that offers the
dedicated bandwidth my killer application needs.

> > But beyond that, there are basic authentication issues that make it 
> > difficult to implement a strong security solution based upon VLANs.
> >
> > Policies controlling access to VLANs depend upon some method of 
> > identifying the client, and it's usually either a MAC address or a 
> > switch port.
>
> 802.1X solutions can go far beyond this.  We can examine 
> credentials on the 
> users computer or the users login to the network.  Or we can 
> just challenge 
> them when they attempt to connect.

Agreed. If they're used. I can also require 2 or 3 factor
authentication, which dramatically strengthens my ability to provide
access controls and audit trails. 

If the business will use them.

> > MAC addresses are readily obtained and almost as easily
> > forged as IP addresses, allowing access to a MAC-based VLAN. 
> Port-based 
> > identification relies on restricted access to the ports 
> themselves, or 
> > to the drop connected to the port.
> >
> > In both cases, bypassing the VLAN security isn't something 
> that happens 
> > by accident, but if you're concerned about security you're 
> planning for 
> > malicious activity. Newer technologies can do stronger 
> authentication 
> > at the port, but aren't widely used. And it's possible to configure 
> > most networking infrastructure to alert you to unexpected changes if 
> > they occur, but this information is rarely incorporated into 
> a security 
> > auditting system, and generally go un-noticed except by the network 
> > group when they're debugging problems.
> >
> > It requires extra diligence to ensure that VLANs provide 
> anywhere near 
> > the security most people expect. In my experience, this 
> extra diligence 
> > doesn't happen, and VLANs are incorrectly understood to 
> provide secure 
> > channels.
>
> Diligence is the key.  It's an important part of the network 
> design process 
> and should be exercised when using any feature.

It's more than just diligence. Networking technology is often selected
by the networking groups in response to pressures they feel to provide
what is felt to be a commodity service, like the phone system. In that
light, the product selected is the one that relieves the most pressure,
and security personnel often isn't involved. Thanks to recent trends in
network attacks (blaster, nachi, etc.), it's getting easier to justify
network security beyond anti-virus on the desktop, but it's still a
tough sell. So the solution is more than dilegence... It requires a
change in the way the network's viewed internally as more than just a
pipe, and co-operation between departments with different goals. Until
then, the diligence simply won't happen, and it's irresponsible to
assume the VLAN is a secure connection.

I spend a lot of my time educating the people I report to and work with
on security issues in the network. While I see a willingness on the part
of vendors to respond to questions concerning network security, it
usually is a result of me pulling rather than them pushing. The next
time you're talking to a client, raise the profile of the security
features. It will make my job a lot easier.

> Liberty for All,
>
> Brian
>
> > > -----Original Message-----
> > > From: Brian Ford [mailto:brford () cisco com]
> > > Sent: Thursday, February 12, 2004 1:14 PM
> > > To: firewall-wizards () honor icsalabs com
> > > Cc: jhall () ptavvs net; Ware, Larry
> > > Subject: Re: Re: [fw-wiz] Vlan's as effective security measures?
> > >
> > >
> > > John,
> > >
> > > And cars crash and cars burn and people are dying in cars all the
> > > time.   And cars can be made to carry disease and explosives
> > > and kill many
> > > people with just one car and driver! So let's all abandon 
> our cars 
> > > and start walking to work every morning.  If we're late the boss 
> > > will understand because cars are dangerous.  ;-)
> > >
> > > You should probably research the switch that you buy and use in 
> > > order to make sure that it doesn't do these things.
> > >
> > > Your mileage may vary!
> > >
> > > Liberty for All,
> > >
> > > Brian
> > >
> > > At 12:00 PM 2/10/2004 -0500, 
> > > firewall-wizards-request () honor icsalabs com wrote:
> > > > Message: 4
> > > > Date: Mon, 09 Feb 2004 12:52:31 -0800
> > > > From: John Hall <jhall () ptavvs net>
> > > > To: "Ware, Larry" <LWare () e-one com>
> > > > Cc: "'firewall-wizards () honor icsalabs com'"
> > > > <firewall-wizards () honor icsalabs com>
> > > > Subject: Re: [fw-wiz] Vlan's as effective security measures?
> > > >
> > > >
> > > > 1.  A surprising number of network devices' VLAN implementations
> > > >     will leak packets between VLANs under heavy loads, 
> or in some
> > > >     cases randomly all the time.
> > > > 2,  Some switches have a single forwarding database 
> which includes
> > > >     VLAN tags and a host presenting a carefully chosen 
> MAC address
> > > >     can sometimes hijack traffic for a host on another
> > > VLAN. 3.  Some
> > > > switches flood ARP requests across VLANs. 4.  Some switches
> > > flood all
> > > > traffic under heavy load. 5.  Few switches and routers have 
> > > > adequate configuration security.
> > > >
> > > > Don't depend on VLANs to guarantee the separation of two
> > > networks that
> > > > *must* be separated.  Your security is only as good as 
> the weakest 
> > > > element in your infrastructure and the security of most
> > > switches (and
> > > > to a lesser extent routers) is pretty weak.
> > > >
> > > > JMH
> > > >
> > > > Ware, Larry wrote:
> > > >
> > > > > Forgive a long out of field, and now working on 
> getting back up 
> > > > > to speed firewall admin, but would someone care to educate me
> > > concerning
> > > > > the security issues related to VLAN's? I have lots of
> > > them, and need
> > > > > to know why a VLAN is not an effective adjunct to firewall
> > > and router
> > > > > security policies. -larry
> > >
> > >
> > > Brian Ford
> > > Consulting Engineer, Security & Integrity Specialist
> > > Office of Strategic Technology Planning
> > > Cisco Systems Inc.
> > > http://www.cisco.com/go/safe/
> > >
> > > The opinions expressed in this message are those of the 
> author and 
> > > not necessarily those of Cisco Systems, Inc..
> > >
> > > This email address is transmitted from San Jose, 
> California, U.S.A..
> > > _______________________________________________
> > > firewall-wizards mailing list firewall-wizards () honor icsalabs com
> > > http://honor.icsalabs.com/mailman/listinfo/firewall-wizards
>
>
> Brian Ford
> Consulting Engineer, Security & Integrity Specialist
> Office of Strategic Technology Planning
> Cisco Systems Inc.
> http://www.cisco.com/go/safe/
>
> The opinions expressed in this message are those of the 
> author and not 
> necessarily those of Cisco Systems, Inc..
>
> This email address is transmitted from San Jose, California, U.S.A..
>
>
> _______________________________________________
> firewall-wizards mailing list firewall-wizards () honor icsalabs com
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