What does the -F flag in Nmap do?

• A. It floods the network with packets.
• B. It enables verbose output.
• C. It performs OS detection.
• D. It specifies a fast scan that limits the number of ports scanned from 1,000 to 100.

Answer: (D)

Understanding how Nmap controls scan speed and scope. The -F flag activates a fast scan mode by using a pre-defined, smaller set of ports—the top 100 commonly used ports—instead of scanning the full default range (about 1,000 ports). This speeds up the scan and gives you a quick overview of likely open services, but it can miss services running on ports outside that list. This option is different from enabling verbose output, OS detection, or sending a flood of packets, each of which is a separate feature or tactic. So, -F is best described as a fast scan that limits the ports scanned to roughly the top 100.