The answer is to synchronize all client workstation clocks using a centralized NTP server. This is correct because Kerberos authentication is fundamentally time-sensitive, relying on synchronized clocks between clients and domain controllers to prevent replay attacks; RFC 4120 defines a default maximum time skew tolerance of 5 minutes, so a client drift of up to 10 minutes will cause ticket requests to be rejected as invalid. On the CISSP exam, this scenario tests your understanding of Kerberos’s dependency on time synchronization within the Access Control domain, often appearing as a trick where you must distinguish between client-side drift and server-side clock issues. A common trap is assuming domain controller clocks are the sole problem, but the real failure point is the client exceeding the skew threshold. Memory tip: think “Kerberos hates drift” — if the clock skew exceeds 5 minutes, the ticket is dead on arrival.
CISSP Identity and Access Management Practice Question
This CISSP practice question tests your understanding of identity and access management. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
A large enterprise uses Active Directory for authentication. Several users report intermittent authentication failures when accessing internal web applications. The help desk confirms that the failures occur at random times and affect both new and existing users. The security team discovers that the system clocks on domain controllers are within acceptable limits, but some client workstations show time drift of up to 10 minutes. The Kerberos protocol is used for authentication. What is the most likely cause of the authentication failures, and what action should be taken?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Synchronize all client workstation clocks using a centralized NTP server
Kerberos authentication relies on synchronized clocks between clients and domain controllers, with a default maximum time skew tolerance of 5 minutes (RFC 4120). A client clock drift of up to 10 minutes exceeds this tolerance, causing intermittent authentication failures because Kerberos ticket requests are rejected as invalid or replay attacks. Synchronizing all client workstations to a centralized NTP server resolves the time skew and restores Kerberos authentication reliability.
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.
✗
Implement password complexity policies to reduce authentication errors
Why it's wrong here
Password complexity does not affect Kerberos time skew issues.
✗
Enable NTLM fallback authentication for the web applications
Why it's wrong here
NTLM is less secure and should not be used as a permanent solution.
✓
Synchronize all client workstation clocks using a centralized NTP server
Why this is correct
Proper time synchronization resolves Kerberos time skew issues.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure Kerberos ticket lifetimes to 24 hours to reduce sensitivity to time skew
Why it's wrong here
Increasing ticket lifetime does not fix the root cause and may increase attack surface.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think increasing Kerberos ticket lifetimes or enabling NTLM fallback will solve the issue, but they overlook the strict time synchronization requirement that is fundamental to Kerberos protocol security.
Detailed technical explanation
How to think about this question
Kerberos uses timestamps in authenticators to prevent replay attacks; the KDC compares the client's timestamp to its own clock, and if the difference exceeds the configured skew (default 5 minutes in Windows), the request is rejected. The time drift of 10 minutes means that even if the domain controllers are synchronized, the client's clock is too far off, causing intermittent failures because the drift may vary or be corrected temporarily by manual adjustments. In real-world scenarios, this often occurs when workstations are not configured with an NTP client or are using a local CMOS clock that drifts over time.
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.
TExam Day Tips
→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 security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Identity and Access Management — This question tests Identity and Access Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Synchronize all client workstation clocks using a centralized NTP server — Kerberos authentication relies on synchronized clocks between clients and domain controllers, with a default maximum time skew tolerance of 5 minutes (RFC 4120). A client clock drift of up to 10 minutes exceeds this tolerance, causing intermittent authentication failures because Kerberos ticket requests are rejected as invalid or replay attacks. Synchronizing all client workstations to a centralized NTP server resolves the time skew and restores Kerberos authentication reliability.
What should I do if I get this CISSP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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