A penetration tester runs a network scan but has some issues accurately enumerating the vulnerabilities due to the following error: OS identification failed Which of the following is most likely…

The correct answer is D. The scan cannot gather one or more fingerprints from the target. OS identification in tools like Nmap relies on fingerprinting techniques, which analyze response characteristics (e.g., TCP/IP stack behavior). If the system is configured to block ICMP responses, or if certain ports are closed, fingerprinting fails. Some modern firewalls and…

Submitted by lukas.cz· Mar 6, 2026Vulnerability Discovery and Analysis

Question

A penetration tester runs a network scan but has some issues accurately enumerating the vulnerabilities due to the following error:

OS identification failed Which of the following is most likely causing this error?

Options

AThe scan did not reach the target because of a firewall block rule.
BThe scanner database is out of date.
CThe scan is reporting a false positive.
DThe scan cannot gather one or more fingerprints from the target.

How the community answered

(31 responses)

A
6% (2)
B
3% (1)
C
3% (1)
D
87% (27)

Explanation

OS identification in tools like Nmap relies on fingerprinting techniques, which analyze response characteristics (e.g., TCP/IP stack behavior). If the system is configured to block ICMP responses, or if certain ports are closed, fingerprinting fails. Some modern firewalls and intrusion prevention systems (IPS) interfere with OS fingerprinting by modifying packet responses.

Topics

#Network scanning#OS fingerprinting#Scanner errors#Vulnerability enumeration

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