I'm currently studying a peneteration/hacking course. I am trying to use nmap against a target to find all the ports that are filtered.
I thought if I used an ACK-scan nmap would give me all the filtered ports. I used
nmap -sA -p- target
and the result was All the 65535 ports scanned are unfiltered. Is this even reasonable? What other scans can I use to complement my first scan?