Which option yields a rapid scan of roughly the 100 most common ports, and how can you disable DNS resolution for speed?

• A. -F performs a fast scan of the 100 most common ports; this option always performs DNS resolution.
• B. -F performs a fast scan of the 100 most common ports; use -n to disable DNS resolution.
• C. -A performs a fast scan of the 100 most common ports; it also enables OS detection.
• D. -p all and -n to disable DNS.

Answer: (D)

The idea being tested is how to get a quick sweep of the most commonly used ports while turning off DNS lookups to keep things fast. The fast scan mode in Nmap targets a predefined set of about the top 100 ports, which speeds things up compared to scanning all ports. DNS resolution is the process of translating IPs and hostnames, and it can slow down scans because Nmap may perform reverse lookups. You can tell Nmap not to do those lookups with the -n option.

So, to achieve both a rapid top-100 port scan and no DNS lookups, run something like: nmap -F -n .

Why the other ideas don’t fit: using a broad set like all ports would be much slower, defeating the rapid scan goal. The aggressive scan option (-A) expands checks beyond a quick top-port list and isn’t about speed in the same way. And claiming that the fast scan always performs DNS resolution ignores the fact that -n disables DNS lookups, which is exactly how you speed things up.