Closed Ports

[pnrdrmmr]

So, I feel like this is a dumb question, but I would like some clarification just in case. When a port is closed, you cannot access information through said port, correct?

The reason I ask is, I work for an internet security company, and one of our managers told a customer that we aren't looking for closed ports, we are looking for filtered ports. Because we can still access and use closed ports. Is it possible he was confusing it with stealthed ports? I feel like what he said was completely wrong, but I don't know enough about networking to be sure. Any information on this topic would be appreciated.

Thanks in advance!

 

[kaa0653]

The difference between closed and filtered is how the reply is handled. Closed ports will reply stating that the connection is denied. Filtered ports will not reply. That is for TCP. UDP is connectionless and for ports that are not open the system with respond with an ICMP port unreachable message. To my knowledge, someone may be able to get through using an existing open port, but once a port is closed you can't use it.

 

[pnrdrmmr]

Thanks so much. That's what I thought.