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RE: Nmap/netwag problem.
From: "Paul J Docherty" <PJD () portcullis-security com>
Date: Thu, 11 Aug 2005 16:07:41 +0100

Whilst the points you are making are correct once you have discovered
open ports, I think you have raced ahead of the question, which was I
think, "which port scanner is giving the correct results?" As many
others have elegantly answered use a packet sniffer and look at the raw
data to see what's going on. You have raced ahead and are bordering
service discovery rather than port status, as we know there can be any
number of filtering devices between the two ends, however, within TCP,
which is what we are talking about here, an open port will respond to a
syn with a syn/ack.

As for scan methods, I tend to use both syn and full (where time
permits) if time is not the key, I prefer to syn scan first then TCP
Connect.  

With regards answering the questions you could, if you are not happy
with the sniffer options use something like hping2(3) and watch the
flags ie

Hping2 -n -V -S -p (port no.) IP_address

Paul.

-----Original Message-----
From: Pete Herzog [mailto:lists () isecom org] 
Sent: Wednesday, August 10, 2005 8:10 PM
To: Kaj Huisman
Cc: Aleph One; pen-test () securityfocus com; Security-Basics
Subject: Re: Nmap/netwag problem.

Kaj,

Anyway. a 'full connect' scan (one that performs the complete
three-way
handshake will _always_ (?) be the most reliable.
My sugeestion is to perform either a nmap connect scan on the ports
from
both results or to manually telnet to the ports and see the response.

The best method for scanning is always to verify responses of a service
behind the ports by using the proper protocol.  Barring that, verify the
types of packets which return, the consistency of their return, delays
in return, and the TTLs.  But using telnet to visit a non-telnet port is
no longer a reliable method.


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