312-50V11 · Question #628
Which of the following command line switch would you use for OS detection in Nmap?
The correct answer is B. -O. The nmap -O flag enables the OS detection engine, which sends specialized probes and compares responses against a fingerprint database to identify the target operating system.
Question
Which of the following command line switch would you use for OS detection in Nmap?
Options
- A-D
- B-O
- C-P
- D-X
How the community answered
(14 responses)- B86% (12)
- C7% (1)
- D7% (1)
Why each option
The nmap -O flag enables the OS detection engine, which sends specialized probes and compares responses against a fingerprint database to identify the target operating system.
The -D flag is used to specify decoy IP addresses during a scan to obscure the true source of the scan, not for OS detection.
The -O switch activates nmap's OS detection subsystem, which sends a series of TCP, UDP, and ICMP probes with varying flags and options to elicit responses that reveal the target's TCP/IP stack implementation. Nmap then matches the observed response patterns against its fingerprint database to determine the OS and version. This flag requires at least one open and one closed port to generate a reliable fingerprint comparison.
The -P flags (such as -Pn, -PS, -PA) control host discovery and ping behavior, not operating system fingerprinting.
The -X flag is not a recognized nmap command-line option and has no defined function in the nmap tool.
Concept tested: Nmap OS detection flag (-O) usage
Source: https://nmap.org/book/man-os-detection.html
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