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Filtered Ports

Posted on 2013-05-23
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Last Modified: 2013-06-06
On a security scan what is a filtered port?  If a port the host is listening on, should the port be closed?
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Question by:Jack_son_
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by:aadih
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Definitions:

(1) Open Port:  If you send a SYN to an open port, you would expect to receive a
SYN/ACK.

(2) Closed Port: If you send a SYN to a closed port, it will respond back with a RST.

(3) Filtered Port: Presumably, the host is behind some sort of firewall.  Here, the
packet is simply dropped and you receive no response (not even a RST).

For a listening port (a little long) look here:

http://www.howtogeek.com/howto/28609/how-can-i-tell-what-is-listening-on-a-tcpip-port-in-windows/ >
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by:Jack_son_
ID: 39191608
Great, thanks for the information.  Should filtered ports be investigated closer or are the open ports the primary risk?
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aadih earned 500 total points
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Open ports.
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