Exam PT0-002 topic 1 question 38 discussion

When Nmap returns that all 65,535 ports are filtered, it means that the network device or firewall is actively blocking the Nmap scan by not allowing any incoming connections to be established. This is a common security measure to prevent unauthorized access or network reconnaissance. This can be done by a firewall or an Intrusion Prevention System (IPS) which is designed to detect and prevent malicious activity on a network. Option B, unsupported flags, is unlikely as Nmap is a widely used tool and the flags used in the command you provided are commonly used for performing an OS fingerprinting and service detection scan. Option C, The edge network device was disconnected, is unlikely as the response of all ports being filtered suggests that the device is actively responding and blocking the scan. Option D, The scan returned ICMP echo replies, is unlikely as the flags used in the command is for OS fingerprinting and service detection scan which does not use ICMP echo replies.

A is correct.

The Nmap command nmap -O -A -sS -p- 100.100.100.50 performs an OS detection (-O), enables advanced and aggressive scan options (-A), performs a SYN scan (-sS), and scans all 65,535 ports (-p-). If the result of this scan was that all ports were reported as filtered, it suggests that something on the network was blocking the scan attempts. Among the options provided, the scenario that best explains this result is: A. A firewall or IPS (Intrusion Prevention System) blocked the scan.

"-O" enables operating system detection. "-A" enables aggressive scanning and includes additional information gathering and script scanning. "-sS" specifies a SYN scan, which is a type of TCP scan. "-p-" scans all 65,535 ports. When the scan results indicate that all ports are filtered, it means that the scanning packets sent by Nmap did not receive any response from the target device. This typically occurs when a firewall or an IPS is in place and actively blocking the incoming scan packets.

Firewall blocked it, add the -Pn and run it again

Since the tester ran another scan and the 65,535 ports where filtered, this shows the firewall is blocking the icmp traffic. The tester would have included -Pn switch to avoid pinging the target. This will show more open ports.