Re: Firewalls and PCI
- From: "Jon R. Kibler" <Jon.Kibler@xxxxxxxx>
- Date: Wed, 16 Jan 2008 18:31:14 +0000
Brian Johnson wrote:
How does a lack of DHCP let you KNOW who is on your network? Absent
DHCP all an attacker with zero knowledge of the network configuration
needs to do is sniff the ARP and other broadcast traffic to determine
the addressing of the network and find themselves an open address or
takeover a used address. Now if you have 802.1x or use IPSEC to limit
communications that is another story entirely and can still function
A number of clients I visit say that lack of DHCP is a security
measure. If they push back on my claim it would only slow an attacker
down I demonstrate just how easy it is to find an open address, I end
up able to talk to their network inside of 5 minutes.
I agree completely that a lack of DHCP does not mean security. However,
anything DHCP I automatically presume is untrustworthy. With static IPs,
I lock down switches, associating a MAC with a port or use 802.1x.
Since you mentioned it, a comment about IPSec: You not believe the number
of sites that think they have IPSec enabled, but don't really. They take
the average windows defaults in IPSec setup (no AH, no ESP) and think
they now have IPSec security. Like everything else, unless configured
correctly, and TESTED, IPSec is not going to provide any additional
security. When a site enables IPSec, you would think they would at least
sniff the network to see if the traffic is REALLY encrypted, but I have
yet to see any site have actually tested their IPSec configuration.
Jon R. Kibler
Chief Technical Officer
Advanced Systems Engineering Technology, Inc.
Charleston, SC USA
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