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A penetration tester is analyzing a Python script that uses the 'paramiko' library to automate SSH key-based authentication across multiple servers. The script fails with 'AuthenticationException' for some servers that the tester is certain have the correct private key configured. Which of the following is the most likely cause of this failure?

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A penetration tester is analyzing a Python script that uses the 'paramiko' library to automate SSH key-based authentication across multiple servers. The script fails with 'AuthenticationException' for some servers that the tester is certain have the correct private key configured. Which of the following is the most likely cause of this failure?

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Answer choices

Why each option matters

Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.

A

Distractor review

The servers are running a different SSH version.

Paramiko supports multiple SSH versions, so this is unlikely to cause the error.

B

Distractor review

The public key is not in the server's authorized_keys file.

The tester is certain the correct key is configured, so this is not the issue.

C

Best answer

The SSH server host key is not in the known_hosts file.

Correct. Paramiko verifies host keys by default; if the host key is not known, it raises AuthenticationException to prevent man-in-the-middle attacks.

D

Distractor review

The username specified is incorrect.

If username were incorrect, the error would be different, such as 'Authentication failed' after trying all methods.

Common exam trap

Common exam trap: answer the scenario, not the keyword

Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.

Technical deep dive

How to think about this question

This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.

KKey Concepts to Remember

  • Read the scenario before looking for a memorised answer.
  • Find the constraint that changes the correct option.
  • Eliminate answers that are true in general but not in this case.
  • Use explanations to understand the rule behind the answer.

TExam Day Tips

  • Underline the problem statement mentally.
  • Watch for words such as best, first, most likely and least administrative effort.
  • Review why wrong options are wrong, not only why the correct option is correct.

Related practice questions

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More questions from this exam

Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.

Question 1

A penetration tester is writing the executive summary for a report. The client's CEO needs to understand the business impact of a critical SQL injection vulnerability. Which of the following should the tester include?

Question 2

A penetration tester has gained a low-privileged shell on a Linux server. During enumeration, the tester discovers a binary with the SUID bit set that belongs to root and is known to have a buffer overflow vulnerability. What is the MOST effective next step to escalate privileges?

Question 3

A penetration tester is performing passive reconnaissance against a target domain. Which of the following resources can be used to gather information about the target without directly sending packets to the target's network? (Select two.) (Choose 2.)

Question 4

A penetration tester has obtained a TGT from a domain controller by cracking the krbtgt hash. Which attack can the tester now perform to gain persistent administrative access to any resource in the domain?

Question 5

A penetration tester is writing the executive summary for the final report. The CEO needs to understand the overall risk level and the business impact of the findings. Which of the following should be included in the executive summary?

Question 6

A penetration tester is writing the executive summary of a penetration test report. Which of the following elements is MOST important to include for a non-technical audience?

FAQ

Questions learners often ask

What does this PT0-002 question test?

Read the scenario before looking for a memorised answer.

What is the correct answer to this question?

The correct answer is: The SSH server host key is not in the known_hosts file. — Paramiko's SSHClient by default checks the server's host key against the local known_hosts file. If the host key is not present or mismatched, it raises an AuthenticationException before even attempting key-based authentication. This is a security feature. The fix is to either add the host key to known_hosts or set missing_host_key_policy to AutoAddPolicy (not recommended in production).

What should I do if I get this PT0-002 question wrong?

Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.

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