You are instructed to perform a TCP NULL scan.

TCP NULL scanning is a stealth scanning technique covered in CEH v13 Reconnaissance and Network Scanning. In a NULL scan, all TCP flags are set to zero. According to RFC 793 and CEH documentation, closed ports must respond with a TCP RST (Reset) packet.

If the port is open, the target typically does not respond, making this technique useful for firewall evasion. Therefore:

RST response = Closed port

No response = Open or filtered port

Other options do not apply to NULL scans:

SYN/ACK is associated with SYN scans.

ICMP errors may indicate filtering, not port state.