That would depend on the port and what function it serves. For example, you
might show port 25 as open because they have an SMTP server and it is not
behind a firewall.
Here is a definition of the different states, straight from the nmap man
page:
"The state is either "open", "filtered", or "unfiltered". Open
means that the target machine will accept() connections on that
port. Filtered means that a firewall, filter, or other network obstacle is
covering the port and preventing nmap from determining whether the port
is open. Unfiltered means that the port is known by nmap to be
closed and no firewall/filter seems to be interfering with nmap's
attempts to determine this. Unfiltered ports are the common case and are
only shown when most of the scanned ports are in the filtered state."
Hope this helps.
Steve Fletcher
MCSE (NT4/Win2k), MCSE: Security (Win2k), HP Master ASE, CCNA, Security+
safletcher@insightbb.com
-----Original Message-----
From: Shand [mailto:shand@adelphia.net]
Sent: Wednesday, March 30, 2005 2:33 PM
To: Steve Fletcher; security-basics@securityfocus.com
Subject: Re: Scanning--more then one side to the argument
External scans.
Against customer using our internet service.
Does a port have to show as "open" or can they for usability show only as
filtered, closed?
Thoughts?
Shand
----- Original Message -----
From: "Steve Fletcher" <safletcher@insightbb.com>
To: "'Sherman Hand'" <shand@adelphia.net>;
<security-basics@securityfocus.com>
Sent: Wednesday, March 30, 2005 3:18 PM
Subject: RE: Scanning--more then one side to the argument
I have a question regarding this. Are you talking about doing an external
scan or an internal scan? I assume an external, because an internal scan
should show a LOT of open ports.
I would say that any open port POTENTIALLY could be a security issue
waiting
to happen, but common sense dictates that some ports must be open for
usability reasons. Plus, if you're going to follow this line of thought,
the fact that the systems are connected to the Internet AT ALL poses a
potential risk. Or, just being networked could be a risk. Or, being
powered on poses a potential risk.
So, based on this, sure it COULD be a security risk waiting to happen, but
more information needs to be gathered to determine the true extent of the
risk. And, it must be reevaluated at regular intervals to catch new
issues
that might have come up since the last scan. What is safe now might not
be
6 months from now.
Hope this helps.
Steve Fletcher
MCSE (NT4/Win2k), MCSE: Security (Win2k), HP Master ASE, CCNA, Security+
safletcher@insightbb.com
-----Original Message-----
From: Sherman Hand [mailto:shand@adelphia.net]
Sent: Wednesday, March 30, 2005 5:05 PM
To: security-basics@securityfocus.com
Subject: Scanning--more then one side to the argument
There has been a on going discussion about the scanning results on our
customers.
Thought one says that "any" port on a standard nmap, showing as "open" is
a
security risk.
Thought two says, no since some things need to show in a state of open.
Should we be stating that through proactive scan, when we find any port
showing as open, that it is a security issue waiting to happen?
Or only if we can show a issue?
Thoughts?
Shand
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