What is the effect of the -F flag on Nmap's scan speed?

• A. Scanning becomes slower due to more ports being scanned
• B. Scanning speed is unchanged
• C. It disables port scanning
• D. Scanning becomes faster due to fewer ports being scanned

Answer: (D)

Using the -F flag enables fast mode, which makes Nmap scan only the most common ports (traditionally the top 100). Because you’re probing far fewer ports, the total amount of work drops, so the scan finishes much faster. It doesn’t disable port scanning or leave speed unchanged; it just reduces the number of ports checked. The trade-off is that open services on less-common ports may be missed, since you’re not scanning the full range.