RE: Snort on home DSL connection

["Bell, Josh" <josh.bell () guidancesoftware com>]

The problem there is Snort is listening outside my firewall - and since I'm using NAT, that interface will never see a 
packet to/from 192.168.x.x.  It'll only see packets to/from the dynamic IP my ISP gave me.

        -----Original Message----- 
        From: Erek Adams [mailto:erek () snort org] 
        Sent: Thu 12/25/2003 6:33 AM 
        To: Bell, Josh 
        Cc: snort-users () lists sourceforge net 
        Subject: Re: [Snort-users] Snort on home DSL connection
        
        

        On Wed, 24 Dec 2003, Bell, Josh wrote:
        
        > Another Snort newb here...
        >
        > I've set up a Snort box at home so I can have an 'expendable' box to
        > experiment and learn on.  I have an SBC DSL connection.  The DSL line
        > runs into my DSL modem, from there to a little hub, and from there to a
        > Linksys-type router/firewall, where my machines are connected.  It's a
        > PPPoE DSL connection so my IP can and does change rather frequently.
        >
        > On my Snort box, eth0 is connected to the 'inside' network with an
        > RFC1918 address and eth1 is connected to the hub in promiscuous mode.
        > It receives all traffic that hits the hub, the only problem I have is I
        > don't know how to set the HOME_NET variable.  I can't use eth0's IP
        > because that's just a 192.168 address.  Eth1 has no IP and I don't want
        > to statically plug in in there.  Can I use a DNS name?  I have a DYNDNS
        > account which in theory is updated regularly and should be the IP of my
        > router.  If not, is there some way of telling it to use whatever IP is
        > currently assigned to a particular MAC?
        
        Use the 192.158.x.x address as HOME_NET.  After all you're looking to see
        what is coming from the internet (var EXTERNAL_NET !$HOME_NET) that's
        coming at you (PPPoE).  Since Snort doesn't handle PPPoE that well, you're
        better off to listen to the 'inside' interface (192.168.x.x) and see
        what's passing "thru" the router/gateway.
        
        Cheers!
        
        -----
        Erek Adams
        
           "When things get weird, the weird turn pro."   H.S. Thompson
 
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