Portscan from the Inside:

• Portscan from the Inside:

• From another machine inside your network, scan your firewall.

• # nmap -sS -O 192.168.0.1 Starting nmap 3.70 ( http://www.insecure.org/nmap/ ) at 2005-04-01 23:15 EST Interesting ports on 192.168.0.1: (The 1653 ports scanned but not shown below are in state: closed) PORT STATE SERVICE 22/tcp open ssh 53/tcp open domain 135/tcp filtered msrpc 137/tcp filtered netbios-ns 138/tcp filtered netbios-dgm 139/tcp filtered netbios-ssn 445/tcp filtered microsoft-ds 1720/tcp filtered H.323/Q.931 Device type: general purpose Running: Linux 2.4.X|2.5.X OS details: Linux 2.4.0 - 2.5.20 Uptime 0.871 days (since Fri Apr 1 02:21:01 2005)

• Only ports 22/ssh and 53/DNS are open on the inside. The other windows filtered ports (135-445) are to keep windows NetBIOS broadcasts from leaking to outside networks.