RE: FTP Window of opportunity?
From: Stevenson, John G (JGStevenson_at_pier1.com)
Date: 03/24/04
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Date: Wed, 24 Mar 2004 11:57:10 -0600 To: "Jerry Shenk" <jshenk@decommunications.com>, <pen-test@securityfocus.com>
Kind of off-topic, although I'd love for Carolyn to sniff the traffic
and report back, just for our on satisfaction. Anyway, on to my
question: Is this "intentional response" by the raptor firewall really
a good thing? Does it allow the connections to pass 'to' the server or
does it seemingly accept the connections and drop them once the response
is sent to the attacker? Just curious...
John
-----Original Message-----
From: Jerry Shenk [mailto:jshenk@decommunications.com]
Sent: Tuesday, March 23, 2004 9:37 PM
To: pen-test@securityfocus.com
Subject: RE: FTP Window of opportunity?
I'd use a sniffer to log monitor what actual packets are being received
from the "ftp server" to see what scanner is right. It would seem to me
that ISS should be getting something back if it's claiming that the port
is open. You could run a sniffing in the path of the traffic between
the scanning machine and the ftp server and set it to only log the
traffic between that pair.
It seems quite normal to get results back from an automated tool that
conflict with something else. Then the pen tester needs to dig a little
deeper and analyze what actually happened.
BTW, some firewalls (Raptor at least) intentionally respond to all kinds
of crazy traffic. It seems that they intentionally try to confuse an
attacker (or pen tester;) by allowing connections to ports that aren't
really open.
-----Original Message-----
From: C Ryll [mailto:carolynryll@hotmail.com]
Sent: Tuesday, March 23, 2004 4:50 PM
To: pen-test@securityfocus.com
Subject: FTP Window of opportunity?
I recently assessed a system in which I already know its configuration
(and
have full legal rights to). FTP is purposefully not running, as well as
blocked by the firewall.
When I scan with ISS, the FTP port shows up. When I use NMap, it does
not
show FTP's port.
Because of the discrepancy, I tried to manually FTP into the system. It
actually said "Connected...", hung for about 10 seconds, and then said
"Connection Terminated."
(As a baseline, telnet's port is also blocked by the firewall, and does
not
show up in scans - essentially, results for telnet are as expected).
With ISS, I'm assuming that it saw "Connected..." and showed me that
port.
My guess would be that NMap waited around to try something else, but saw
"Connection Terminated" and didn't list it.
However, as I said previously, seeing that it actually says "Connected",
and
then hangs for about 10 seconds before terminating:
1). Can I use this behavior to my advantage somehow? If yes, how?
2). Is there a known explanation to this?
The firewall is the Internet Connection firewall, and I am curious if it
requires the ftp port inadvertently for its functioning when checking
the
incoming packets...
While I can make some changes to the system (like shutting off certain
services and shutting off the firewall), I cannot modify it such that I
can
try another firewall or anything else like that.
Any help is greatly appreciated.
Carolyn.
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