Nmap Development: closed vs filtered in UDP scan

[Paul Johnston <paul () westpoint ltd uk>]

Hi,

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

Paul

--
Paul Johnston
Internet Security Specialist
Westpoint Limited
Albion Wharf, 19 Albion Street,
Manchester, M1 5LN
England
Tel: +44 (0)161 237 1028
Fax: +44 (0)161 237 1031
email: paul () westpoint ltd uk
web: www.westpoint.ltd.uk



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