From: Jose Maria Lopez (jkerouac@eresmas.com)
Date: Fri Sep 03 2004 - 13:19:57 EDT
El mié, 01 de 09 de 2004 a las 19:43, Scovetta, Michael V escribió:
> Vinay,
> I'm not an expert on this, but here's how I would do try:
> #1. How do you know there's a web proxy server in your local network?
> If it is because a resource is restricted by IP and you think
> people are getting in when they shouldn't be, then look through the
> server logs to see who accessed it, and look for anomolies. If you can
> find someone who has used the proxy to go somewhere, then sniff his
> traffic to see where he goes, one of the boxes should be the proxy.
> #2. Scan the network traffic for strings like "nph".
> #3. Scan machines, looking for ones that accept http connections.
>
> Just my $0.02.
I doubt this kind of scannings to find ports 80 responses or
ports 8080 or 3128 open can be useful to find the transparent
proxy in a local network. The trick a good administrator will
use is to have the transparent proxy on the same machine that
does the redirection, closing the 8080 or 3128 port for traffic
from the local network, and only allowing the traffic from
the localhost (redirected traffic), so you can't see the ports
open.
And about finding a device that responds to the 80 port request
you must know the IP direction in first place, and if it's the
firewall it can be configured so it doesn't answer this kind of
questions, just routes the traffic through the 80 port to the
proxy and to and from internet.
If the system is well configured can be quite tricky to find the
transparent proxy. But if you can't find it you can bet it's the
firewall machine or the router (making a tcptraceroute or some
scanning). You have to be just a little lucky to find it.
--
Jose Maria Lopez Hernandez
Director Tecnico de bgSEC
jkerouac@bgsec.com
bgSEC Seguridad y Consultoria de Sistemas Informaticos
http://www.bgsec.com
ESPAÑA
The only people for me are the mad ones -- the ones who are mad to live,
mad to talk, mad to be saved, desirous of everything at the same time,
the ones who never yawn or say a commonplace thing, but burn, burn, burn
like fabulous yellow Roman candles.
-- Jack Kerouac, "On the Road"
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