If you perform a port scan with a TCP ACK packet, what should an OPEN port return?
A.
RST
B.
No Reply
C.
SYN/ACK
D.
FIN
Explanation:
Open ports return RST to an ACK scan.
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A
SORRY B
B is the correct answer.
Reference: http://nmap.org/book/man-port-scanning-techniques.html
But your reference says A.
RST if closed; no response if open of filtered.
It should be B
the correct answer is A, because.. TCP work 3 way handshake..
Since there is no SYN/ACK being happened from the Server to client,
the server will RST the connection if it receive a ACK packet from the initiator.
thats what my understanding 😉
answer A.
Q: you have the right link but the bad answer.
Extract from your link for the ACK SCAN
When scanning unfiltered systems, open and closed ports will both return a RST packet.
The ACK scan is a techinque used to probe the existence of a firewall, so the RST response means that the specific port is not filtered
Open Port -> no reply