RE: DHCP in a corporate MS environment - Security Risk?

["Darden, Patrick S." <darden () armc org>]

Another possibility would be a more secure alternative to DHCP.  
With Radius (just one example) you can require that people authenticate 
off of user database (Unix passwd/shadow file, LDAP, NT Domain, ADS....)

Of course, a sniffer on your network, arp poisoning, etc. would obviate
a lot of the security gains....

--Patrick Darden


-----Original Message-----
From: Ben Nagy [mailto:ben () iagu net]
Sent: Wednesday, January 22, 2003 3:21 AM
To: Eye Am; firewall-wizards () honor icsalabs com
Subject: Re: [fw-wiz] DHCP in a corporate MS environment - Security
Risk?


Put me down as a "me too" for Wes's post.

Static IP assignment for individual clients is insane. If you want
strong(ish) machine-based security then look at switch port MAC filters;
they're also insane from a management point of view but at least they
actually offer a positive security delta.

If you desperately want to write ACLs based on groups of machines then you
may as well use DHCP reservations and start buying antacid in bulk for your
sysadmin. Better, if you're in an MS environment, is to look at something
like a proxy server or an IAS server to do real user-based authentication
(if there's a working non-MS way to do it, someone let me know) based on the
domain or AD. Be sure not to confuse this with a real network-level
firewall, though, it's just a way to do some user restriction that's not
SOCKS. I would expect to see a "proper" firewall as well.

Please ask your security consultant to send us a short note explaining the
risks of "DHCP database compromise". I shall pin it on my wall.

For finer points, I usually do static config on servers (old fashioned), and
I agree that you should get rid of your multihomed in/out devices as soon as
you can.

Cheers,

ben

----- Original Message -----
From: "Eye Am" <eyeam () optonline net>
To: <firewall-wizards () honor icsalabs com>
Sent: Tuesday, January 21, 2003 5:06 AM
Subject: [fw-wiz] DHCP in a corporate MS environment - Security Risk?


> I'm looking for opinions, experiences and references on the subject.
Downed
> and searched the entire Firewall-Wizards list. Found little discussion
> either
> way. This may be a bit OT for the board except that some security may well
> be set at the public-facing firewall as well as risks may be apparent
there.
> Our corporate network is reasonably well set up with private and public
DNS,
> no wireless IP connections and blocking all RFC1918 traffic in or out of
the
> public side. Some security consultants highly recommended static
addressing
> across the board for security and control reasons - i.e.. access-list
> control and the potential for compromise of the DHCP database. I have
> searched google etc and found a few articles and whitepapers.
>
> We have historically configured static IPs on servers, routers, switches
and
> all outside-facing devices. We do have several multi-homed devices with
> static, public IP and a second interface facing inside (these are being
> migrated to DMZ where multi-homing will no longer be necessary.) However
> this does get to be a pain when making across-the-board changes.
> Documentation is a bear as well since we are a small company with little
> resources available to keep detailed network drawings up-to-date.
>
> Lately we are leaning towards regular lease-based DHCP for workstations
and
> reserved DHCP addresses on servers on the private side. This will, of
> course, make life much easier when making widespread changes or additions
> such as adding secondary DNS. I have been wavering back and forth.
>
> Is there any experience with compromised DHCP databases in MS
environments?
> Any strong opinions or reasoning pro or con the use of DHCP? Any
> recommendations for shoring up the service and it's traffic?
>
> Much Appreciated In Advance
> Chuck
>
> _______________________________________________
> firewall-wizards mailing list
> firewall-wizards () honor icsalabs com
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