Firewall Wizards mailing list archives

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


From: Eye Am <eyeam () optonline net>
Date: Sun, 23 Feb 2003 22:01:46 -0500


----- Original Message -----
From: "Eye Am" <eyeam () optonline net>
To: <firewall-wizards () honor icsalabs com>
Sent: Monday, January 20, 2003 11:06 PM
Subject: DHCP in a corporate MS environment - Security Risk?

I'd like to thank everyone for their responses.

Just a note that we did stick with DHCP reservations. There are some nice
benefits since we combined this with more organized addressing schemes.

We have broken up our private address space in blocks by server type and
even physical location. It makes firewall reporting mich easier because I
can report on a range of IP addies and have all FTP or SQL servers, or all
Programming computers' activities on one report.

I suppose eventually we will need to revisit if we run out of addies for
servers in one type or the other, that's no problem.

Chuck


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


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