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RE: DENY x REJECT
From: Frank Knobbe <FKnobbe () KnobbeITS com>
Date: Thu, 4 Oct 2001 14:44:03 -0500

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-----Original Message-----
From: Rosenau [mailto:rosenau () netsec com br]
Sent: Wednesday, October 03, 2001 10:53 AM

Does anybody know a port scanner that could distinguish a 
"deny" filtered
tcp port (firewall drops packets for the port) from a 
"reject" filtered tcp
port (firewall returns an ICMP - port unreachable)?.

Nmap seems to report boths cases simply as "filtered". 
Actually, both cases
are filtered, but when you receive a ICMP, you can be sure 
that the port is
really filtered. If you do not receive nothing, the port 
could be filtered,
or packets could have been lost...


I always run a tcpdump session along with scans to watch for
interesting stuff like that. Also, variations in the responding TTL
will give clues where system are located during sweep scans.

tcpdump is your friend ;)

Regards,
Frank


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