The answer is that a single pre-shared key for all users is the most critical finding because it creates a single point of failure for the entire VPN infrastructure. When a single PSK is shared across every remote connection, compromise of that one key allows an attacker to impersonate any authorized user and gain unrestricted network access, completely bypassing user-level accountability. This scenario tests your understanding of authentication weaknesses in IPsec configurations, a common CISA exam trap where candidates might focus on the shared document or lack of multi-factor authentication, but the core risk is the absence of per-user credentials. Remember, changing a single PSK monthly does not fix the fundamental flaw—without unique authentication per user, the VPN cannot distinguish a legitimate employee from an attacker holding the key. Memory tip: “One key to rule them all” means one key to lose them all.
CISA Protection of Information Assets Practice Question
This CISA practice question tests your understanding of protection of information assets. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
You are an IS auditor reviewing the remote access configuration for a medium-sized enterprise. The company uses a VPN concentrator to allow employees to connect from home. The VPN is configured with IPsec using pre-shared keys (PSK) and requires no multi-factor authentication. Employees use company-issued laptops with full disk encryption. The VPN logs show that connections are coming from a wide range of IP addresses, including some from countries where the company has no business operations. The IT manager argues that the PSK is changed monthly and that full disk encryption mitigates any risk. However, during the audit, you find that the PSK is stored in a shared document on an internal file server accessible to all employees. Additionally, the VPN concentrator uses a single PSK for all users. Which of the following is the MOST critical finding?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The VPN uses a single pre-shared key for all users, increasing the risk of widespread compromise
The use of a single pre-shared key (PSK) for all VPN users is the most critical finding because it creates a single point of failure: if that key is compromised, an attacker can impersonate any authorized user and gain full network access. The fact that the PSK is stored in a shared document accessible to all employees dramatically increases the likelihood of exposure, and changing it monthly does not remediate the fundamental lack of user-level authentication. Without per-user credentials or multi-factor authentication, the VPN concentrator cannot distinguish between legitimate employees and an attacker who possesses the shared key.
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.
✗
The PSK is changed monthly, but the change interval is too long
Why it's wrong here
Monthly change is reasonable, but the real issue is single PSK.
✓
The VPN uses a single pre-shared key for all users, increasing the risk of widespread compromise
Why this is correct
Single PSK creates a single point of failure.
Related concept
Read the scenario before looking for a memorised answer.
✗
Full disk encryption on laptops is not sufficient to protect VPN credentials
Why it's wrong here
Laptop encryption is a separate control.
✗
VPN connections from unexpected countries indicate possible unauthorized access
Why it's wrong here
This is a symptom, not the most critical finding.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates focus on the visible symptom (unexpected IP addresses) or the partial control (monthly PSK rotation) rather than recognizing that a single shared secret for all users is a fundamental architectural flaw that undermines all other controls.
Detailed technical explanation
How to think about this question
IPsec with pre-shared keys uses IKE (Internet Key Exchange) to authenticate peers; with a single PSK, the VPN concentrator performs only a group-level authentication, not per-user authentication. In a real-world scenario, an attacker who obtains the PSK (e.g., via the shared document) can use a tool like strongSwan or a VPN client to establish a legitimate-looking IPsec tunnel, bypassing any user-specific controls. This is why RFC 4301 and NIST SP 800-77 recommend using digital certificates or per-user PSKs combined with multi-factor authentication for remote access VPNs.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Protection of Information Assets — This question tests Protection of Information Assets — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The VPN uses a single pre-shared key for all users, increasing the risk of widespread compromise — The use of a single pre-shared key (PSK) for all VPN users is the most critical finding because it creates a single point of failure: if that key is compromised, an attacker can impersonate any authorized user and gain full network access. The fact that the PSK is stored in a shared document accessible to all employees dramatically increases the likelihood of exposure, and changing it monthly does not remediate the fundamental lack of user-level authentication. Without per-user credentials or multi-factor authentication, the VPN concentrator cannot distinguish between legitimate employees and an attacker who possesses the shared key.
What should I do if I get this CISA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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