312-50V11 · Question #698
Trinity needs to scan all hosts on a /16 network for TCP port 445 only. What is the fastest way she can accomplish this with Nmap? Stealth is not a concern.
The correct answer is A. nmap -p 445 -n -T4 -open 10.1.0.0/16. The fastest Nmap TCP port scan on a large network combines port targeting, disabled DNS resolution, and aggressive timing to maximize speed.
Question
Trinity needs to scan all hosts on a /16 network for TCP port 445 only. What is the fastest way she can accomplish this with Nmap? Stealth is not a concern.
Options
- Anmap -p 445 -n -T4 -open 10.1.0.0/16
- Bnmap -p 445 -max -Pn 10.1.0.0/16
- Cnmap -sn -sF 10.1.0.0/16 445
- Dnmap -s 445 -sU -T5 10.1.0.0/16
How the community answered
(41 responses)- A83% (34)
- B5% (2)
- C2% (1)
- D10% (4)
Why each option
The fastest Nmap TCP port scan on a large network combines port targeting, disabled DNS resolution, and aggressive timing to maximize speed.
Option A uses `-p 445` to limit scanning to only TCP port 445, `-n` to skip DNS resolution which eliminates lookup overhead across 65,536 hosts in a /16 range, `-T4` to apply aggressive timing for faster probe rates, and `--open` (rendered as -open) to display only open ports - together these flags represent the correct combination for fast, targeted scanning when stealth is not required.
`-max` is not a valid Nmap flag, making this command syntactically invalid and non-functional.
`-sn` instructs Nmap to perform a ping sweep only with no port scanning, and the port is not specified with `-p`, so port 445 would never be scanned.
`-s 445` is not a valid Nmap option for specifying a port (the correct flag is `-p 445`), and `-sU` performs a UDP scan rather than the required TCP scan.
Concept tested: Nmap TCP port scan speed optimization flags
Source: https://nmap.org/book/man-briefoptions.html
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