RE: Comparing hosts on a network to text file

[Mike Saldivar <Mike.Saldivar () usurf usu edu>]

Andi,

Do you have control over your network?

Your requirements are already implemented in 802.1x http://en.wikipedia.org/wiki/IEEE_802.1X and other types of 
network-based MAC authentication.

When you get a new machine, you add its MAC to your whitelist on your RADIUS server, and then the network will allow 
that device to connect.  Any unknown MAC will be blocked automatically when it is plugged in.  It won't matter if they 
assign themselves valid IP addresses; they will be blocked upon connection to the network.
And depending on whether you worry about MAC spoofing, you can configure other port security options to block MACs 
appearing on more than one port, more than a specific number of MACs per port, etc.

-Mike

-----Original Message----- 
From: listbounce () securityfocus com [mailto:listbounce () securityfocus com] On
Behalf Of Morris, Andi 
Sent: Tuesday, August 07, 2012 16:38 PM 
To: security-basics () securityfocus com 
Subject: Comparing hosts on a network to text file 

Hi all, 
I'm looking to create a script, or use something already in existence to
scan a network for hosts, returning the mac addresses active on the network.
The script should then compare the mac addresses discovered to a
prepopulated text file and somehow notify me of any discrepancy.

I'd imagine nmap would be the tool I'm after. 

The scenario is: 
I have a network that has a filled DHCP scope. 
When a user registers a device with us we assign them an IP address on the
Windows DHCP server. 
We are trying to avoid users manually giving themselves an IP address from
this range and gaining access. 
My plan was to have a script poll the network every 'n' minutes to compare
the mac addresses on the network to those that we have reserved IPs for and
to email the details of any rogue clients to a designated mailbox .

Does this sound feasible and does anyone know of a tool that would already
exist for this before I spend hours learning and configuring nmap (not time
badly spent I admit).

Cheers, 
Andi 


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