NMAP port states explanation

NMAP port states explanation - TCP SYN -sS

I've always struggled with various port states reported by nmap (http://nmap.org). Different scan types report different port states for listening but firewalled ports, listening accessible ports or not listening and so on.

To make my life easier I decided to create tables of most common scan types. I armored myself with Wireshark and did some testing. I used a Windows Firewall running on the scanned machine (called target) for the purpose of this lab.

Service State: Listening - means that there is a valid service listening on the scanned port
Service State: Not Listening - there is nothing on the scanned port
No Firewall column - firewall is off
Firewall column - scanned port is firewalled

In a SYN scan NMAP attempts to establish a half-open TCP connection (syn + syn,ack + rst,ack).

TCP SYN	Service State	No Firewall			Firewall
-sS	Listening	State: Open			State: Filtered
		nmap target nmap		SYN SYN,ACK RST	nmap target nmap	SYN SYN
	Not Listening	State: Closed			State: Closed
		nmap target	SYN RST,ACK		nmap target	SYN RST,ACK

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#SecureSenses --verbose

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