The correct choice is to examine ~/.ssh/authorized_keys for unauthorized keys. This is because the SSH public key authentication mechanism relies on a list of trusted public keys stored in that file; when a connection attempt uses a valid key, the server logs the key’s fingerprint and the connecting IP, but the key itself must be present in authorized_keys to grant access. Since the user denies connecting from 203.0.113.5, the most likely explanation is that an attacker added their own public key to that file, allowing them to authenticate as root from any IP. On the CHFI exam, this scenario tests your understanding of Linux forensic artifacts related to SSH compromise—specifically, that the auth.log only shows the event, while the authorized_keys file is the definitive evidence of key injection. A common trap is to focus on the IP address or the SSH daemon configuration, but the real forensic pivot is the key file itself. Memory tip: “Keys grant access, logs only show the knock.”
CHFI OS and Network Forensics Practice Question
This CHFI practice question tests your understanding of os and network forensics. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
During a Linux forensic investigation, you find the following entry in /var/log/auth.log: "Accepted publickey for root from 203.0.113.5 port 54321 ssh2: RSA SHA256:abc...". The user claims they never connect from that IP. Which forensic artifact should you examine next to confirm unauthorized access?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "never"
Why it matters: Absolute qualifier. True only if the statement has zero exceptions — be cautious of options that seem obvious but break down in edge cases.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
~/.ssh/authorized_keys for unauthorized keys
The presence of an authorized key from an unknown IP suggests an attacker added their public key. Checking ~/.ssh/authorized_keys on the affected account will reveal any unauthorized keys.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
bash_history for suspicious commands
Why it's wrong here
While useful, bash_history may be deleted or truncated, whereas authorized_keys is persistent.
✗
/etc/shadow for recent modifications
Why it's wrong here
Shadow file contains password hashes; key-based access does not modify it.
✓
~/.ssh/authorized_keys for unauthorized keys
Why this is correct
Unauthorized SSH keys are often added in authorized_keys; this file should be examined for unknown entries.
Clue confirmation
The clue word "never" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
/var/log/syslog for cron job entries
Why it's wrong here
Syslog may show other activity, but the key-based access indicates SSH keys should be checked first.
Common exam traps
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.
Trap categories for this question
Command / output trap
Syslog may show other activity, but the key-based access indicates SSH keys should be checked first.
Detailed technical explanation
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.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the CHFI exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CHFI question in full detail.
Identify which CHFI exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
OS and Network Forensics — This question tests OS and Network Forensics — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ~/.ssh/authorized_keys for unauthorized keys — The presence of an authorized key from an unknown IP suggests an attacker added their public key. Checking ~/.ssh/authorized_keys on the affected account will reveal any unauthorized keys.
What should I do if I get this CHFI question wrong?
Identify which CHFI exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "never". Absolute qualifier. True only if the statement has zero exceptions — be cautious of options that seem obvious but break down in edge cases.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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