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GPEN · Question #44

John works as a contract Ethical Hacker. He has recently got a project to do security checking for in the information gathering step. Which of the following commands will he use to accomplish the task

The correct answer is B. nmap -v -O 208.100.2.25. The nmap command with the -O flag performs OS fingerprinting and is a standard information-gathering technique. Plain netcat connections to individual ports do not provide systematic host enumeration.

Penetration Testing Foundations & Reconnaissance

Question

John works as a contract Ethical Hacker. He has recently got a project to do security checking for in the information gathering step. Which of the following commands will he use to accomplish the task? Each correct answer represents a complete solution. Choose two.

Options

  • Anc 208.100.2.25 23
  • Bnmap -v -O 208.100.2.25
  • Cnc -v -n 208.100.2.25 80

How the community answered

(35 responses)
  • A
    9% (3)
  • B
    71% (25)
  • C
    20% (7)

Why each option

The nmap command with the -O flag performs OS fingerprinting and is a standard information-gathering technique. Plain netcat connections to individual ports do not provide systematic host enumeration.

Anc 208.100.2.25 23

The command 'nc 208.100.2.25 23' opens a raw TCP connection to the Telnet port only and does not enumerate ports, fingerprint the OS, or gather broader host information.

Bnmap -v -O 208.100.2.25Correct

The command 'nmap -v -O 208.100.2.25' performs a verbose OS fingerprinting scan against the target, identifying the operating system type, version, and open services through TCP/IP stack analysis. This yields structured host intelligence - OS identity, open ports, and service versions - which is the primary goal of the information-gathering phase in a security assessment.

Cnc -v -n 208.100.2.25 80

The command 'nc -v -n 208.100.2.25 80' connects only to HTTP port 80 and at most retrieves a single service banner, providing no OS-level fingerprinting or multi-port enumeration needed for comprehensive information gathering.

Concept tested: Nmap OS detection for network information gathering

Source: https://nmap.org/book/man-os-detection.html

Topics

#banner grabbing#nmap OS detection#netcat#information gathering

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