Am Sonntag, den 19.02.2006, 10:34 +0530 schrieb Neil:
gigabit@satx.rr.com wrote:
ok, some background...
i have transfered from network engineering to the information security
group for my company, which is mid-sized with about 2000 employees
across 90 locations (financial).
the lessons learned from being in network engineering is that they are
first and foremost concerned with maintaining the production
environment. the management processes/procedures are completely
disregarded if it is deemed necessary to "get something done".
as i try to build out a security plan for how to deal with
servers/routers/end users, i keep coming to the conclusion that it will
be meaningless unless control can be taken over what the other
department is doing (network engineering). the one commonality for all
devices on the network is that they have an IP address.
i would like to propose to management that dhcp should be disabled, so
as to force the building of a database that will hold all of the
information needed to begin a comprehensive security policy. the
security group would manage the database to ensure that we are
collecting information (such as O/S, IOS version, anti-virus
compliance...)
i realize this will incur more work for those poor souls that have to
deploy hardware, but i believe the benefits out-weigh the costs. the
benefits i see:
1. once a branch location is staticly addressed, we have a working
inventory of what is out there.
2. a more secure environment. no longer can users bring in non-
company owned devices and place them on our production network (which
is already a policy---that isn't policed).
3. i can setup automated scripts that check MAC addresses to IP
addresses on the router ARP tables to check for spoofing.
our branch locations don't change very often.....some are still on
token ring for god's sake, so i don't really see that much more
workload.
Has anyone else dropped DHCP as a management/compliance decision?
thanks.
Well, let me start by saying that dropping DHCP is a teeny tiny step
towards making your network more secure: every device that can use DHCP
probably has an option to put in manual IPs...so they pick one and
assign it, and they're in all the same.
On the other hand, yes, with static IPs, you could assign various
permissions by IP, which you couldn't do with DHCP if the addresses
changed. Of course, assigning by IP is about as secure as assigning by
hostname (in the sense that if someone could take down the original
owner, they could step into that spot and get all associated permissions).
Just a 2p thought:
My suggestion would be to use DHCP with MAC-based reservations.
Isn't it right that any wannebe hacksor can easily spoof his/her
mac-address to let it look like an "authorised" one? And wouldn't this
mean that the only barrier to get an IP is to choose/find a correct
mac-address, which might be done by sniffing the network or something
alike? If so, giving away Ips based on mac-addresses doesn't look too
secure to me, does it?
Greets, Andreas
This
would be like static addresses, except that you could manage it
centrally (allowing you to change an IP address if you had need for
whatever reason), and gives you the convenience of DHCP for visitors or
whatnot. You could also probably rig something to check every IP
against its reservation, which would let you see if you had any
intruders on the network whose computers automatically grabbed an IP
(since everything is automatic these days...).
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--
Andreas Hell <anhell@gmx.de>
---------------------------------------------------------------------------
EARN A MASTER OF SCIENCE IN INFORMATION ASSURANCE - ONLINE
The Norwich University program offers unparalleled Infosec management
education and the case study affords you unmatched consulting experience.
Tailor your education to your own professional goals with degree
customizations including Emergency Management, Business Continuity Planning,
Computer Emergency Response Teams, and Digital Investigations.
http://www.msia.norwich.edu/secfocus
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