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Re: closed vs filtered in UDP scan
From: Bo Cato <jcato73 () comcast net>
Date: Tue, 7 Oct 2003 13:45:13 -0400

Filtered refers to the fact that if a device or software between the
scanner and scanned host is filtering then an ICMP won't be generated by
the scanned host. A non-response could mean open or filtered. You may
want to research general firewall packet filtering for a more detailed


Hello Paul,

Tuesday, October 07, 2003, 12:47:30 PM, you wrote:

PJ> Hi,

PJ> What exactly does open/closed/filtered mean in a UDP scan? I thought the 
PJ> test was just to send to the UDP port, and look for an icmp port 
PJ> unreachable message. If it appears the port is closed, otherwise we 
PJ> guess that it's open. Where does filtered come from?

PJ> Thanks,

PJ> Paul

Best regards,
 Bo                            mailto:jcato73 () comcast net

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