Penetration Testing mailing list archives
Re: firewall question
From: "Dario N. Ciccarone" <dciccaro () cisco com>
Date: Thu, 14 Feb 2002 17:12:03 -0300
It seems to me that a lot of people use either nat or pat and that these types of firewalls by default drop unsolicited connection attempts (meaning packets that arrive with the syn bit set). Any packet that leaves the network is put in the state table so that the return packets can come back in. My question is this; if I were to exploit a client-side buffer overflow and I got the system to make a connection to me via netcat with a destination port of 80, would I circumvent a majority of the stateful inspection firewalls? It seems
depends on configuration. you can block all outgoing traffic, or force the user to authenticate to the firewall before been allowed to go out.
that these firewalls trust that ALL connections originating from the inside are good. Now I know we could block off destination ports of services we don't want to allow access to (say no port 23 traffic leaves the network because we don't allow telnet) but I am wondering if either of these firewalls have a method of filtering based on protocol (for example allow 80 to be a destination port but only http traffic can cross it. No netcat, no aim, no limewire just http.
that would be a proxy type firewall. PIX and Checkpoint are both stateful packet filters. a proxy firewall can inspect the traffic, and upon realizing it's not HTTP (it's not conformant to spec) it could drop it. of course, nothing prevents you of using something like httptunnel . . . ---------------------------------------------------------------------------- This list is provided by the SecurityFocus Security Intelligence Alert (SIA) Service. For more information on SecurityFocus' SIA service which automatically alerts you to the latest security vulnerabilities please see: https://alerts.securityfocus.com/
Current thread:
- firewall question leon (Feb 14)
- Re: firewall question Rzac` (Feb 14)
- Re: firewall question Michael Starr (Feb 14)
- Re: firewall question John Adams (Feb 14)
- Re: firewall question dr . kaos (Feb 14)
- RE: firewall question Panos Dimitriou (Feb 15)
- <Possible follow-ups>
- Re: firewall question Dario N. Ciccarone (Feb 14)
- RE: firewall question Matt Peterson (Feb 15)
- Re: firewall question dr . kaos (Feb 15)