Which flag would you use to perform operating system detection via TCP/IP fingerprinting?

• A. -F
• B. -sV
• C. -p-
• D. -O

Answer: (D)

OS detection via TCP/IP fingerprinting works by sending crafted probes and analyzing how the target responds—looking at patterns like TTL, window size, TCP options, and acknowledgment behavior to infer the operating system. In Nmap, this capability is enabled with the -O flag, which activates TCP/IP fingerprinting and matches the observed response patterns against known OS fingerprints. The other options serve different purposes: -sV focuses on service and version detection, -F performs a fast scan, and -p- scans all ports. Therefore, to perform operating system detection via TCP/IP fingerprinting, you would use the -O flag.