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Re: Locking down Ports and DHCP
From: "Dahl, Kevin" <Kevin.Dahl () ARS USDA GOV>
Date: Thu, 5 Aug 2010 12:26:16 -0600

How do those of you who are using 802.1x solve the problem with patching
and/or nightly backups ??

K-Dee


-----Original Message-----
From: pauldotcom-bounces () mail pauldotcom com
[mailto:pauldotcom-bounces () mail pauldotcom com] On Behalf Of Jody &
Jennifer McCluggage
Sent: Thursday, July 29, 2010 8:00 PM
To: 'PaulDotCom Security Weekly Mailing List'
Subject: Re: [Pauldotcom] Locking down Ports and DHCP

I agree with Tim about recommending  802.1x.  You can set it up so that
the switches will not allow access until the end-user authenticates
themselves on the network (via Windows RADIUS service, IAS,
communicating with a domain controller).  The 8021.X clients on Windows
XP SP3 and higher are pretty stable (it will work on lower versions but
SP3 added some 802.1x improvements). As Tim pointed out, more and more
embedded devices such as printers are now also supporting 802.1x.  For
other embedded devices (older printers, copiers, UPS,  etc), you can
utilize MAC address filtering.  This is less of an issue with these
since they tend to be fairly static (i.e.
they won't be moving around much) and usually have some additional
compensating physical controls.  You will probably want to use MAC
Address filtering with your servers too. 802.1x tends not to work well
with servers since it requires authentication prior to granting port
access.  If someone has physical access to the ports that your servers
are using, port
authentication is the least of your problems!     

Also as Tim said, keep in mind that you are adding some additional
moving parts so more things can go wrong (8021.x client issues, switch
issues, or RADIUS server issues - over the years I have had to deal with
all three at one time or another but nothing real major).  That being
said, except for the occasional minor headache,  I have had very little
issues with it over the years. Also keep in mind that the workstation
will not have access to the network until the user authenticates with an
approved domain level account.  

Let me know If you want some examples on how to set up using Cisco
switches and Windows workstations and radius/domain server.

Jody

  

-----Original Message-----
From: pauldotcom-bounces () mail pauldotcom com
[mailto:pauldotcom-bounces () mail pauldotcom com] On Behalf Of Bugbear
Sent: Thursday, July 29, 2010 9:04 AM
To: PaulDotCom Security Weekly Mailing List
Subject: Re: [Pauldotcom] Locking down Ports and DHCP

First and foremost get your company policies and procedures in place if
you have not yet. Also, you will need "buy in" from the support staff
because their helpdesk calls are going to increase.

With that said, I would look at 802.1x

Assuming you are a Windows shop and your switches support it (most
modern switches do), take a look. I have leveraged it somewhat
successfully. I personally do not do any NAP/NAC (remediation), I just
very simply use Radius to auth the domain computers and domain users.
If joined to the domain and a member of this group then they are on the
production LAN, if not the switches will dynamically VLAN them to a
Quarantine VLAN.

What you do with "guests" is up to you from there. You can wait for the
helpdesk call or you could provide restricted internet access. If the
later, consider the appropriate egress filtering, logging, alerting,
IDS, etc...
Also consider using PAT to give that network a unique public IP. Lastly,
consult your legal team to draw up some language for "guests" to click
through via Web Auth/Captive Portal (most modern switches support this
too).
The language should note that your Company is not responsible / liable
and you hold the right to monitor unencrypted traffic on the network
(careful with what type of monitoring - headers verse full content)

Most Printers, Scanner, AP's etc.. support 802.1x these days. An
alternative (not a very good one) would be port security via the mac
addr (but that will only keep the layman off).

Now the part your probably going to struggle with. The supplicant.
There are many. MS Windows XP SP3 and above has one built in and
supports GPO control. There are also products like Juniper/Odyssey and
Cisco Clean Access (Which i think just got EOL).

They all suck (excuse me have their limitations). The Windows supplicant
in Windows 7 seems to have been approved quite a bit however. In XP
there were issues with legit end users being temp flipped to quarantine
(while radius auth's them < the default behavior). Once flipping back
and the DHCP client will sometimes not get an updated IP for that
subnet. To date I have not found a workaround, except Windows 7.

Also, if your admins are using logon scripts and not doing so through
GPO they will need to as they will not run post Auth

Other tech out there includes tracking/alerting after the fact (someone
being on your network).

Hope this helps

Tim



On Wed, Jul 28, 2010 at 5:36 PM, Tyler Robinson
<pcimpressions () gmail com>
wrote:
I am coming into an environment of over 1000 clients everything is 
setup DHCP except printers and servers I am trying to work towards a 
much more secure network but am at a loss of how to start locking down

switches and DHCP I want to make sure no one is plugging in 
unauthorized devices or rogue devices for that matter so just 
wondering how everyone else is securing there networks as always 
pauldotcom listeners are the best and all help is welcomed.

TR

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