hardMultiple ChoiceObjective-mapped
CISA Practice Question: An IS auditor reviewing the remote access…
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?
⚠ Common exam trap
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.
Answer choices
Why each option matters
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.
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.
- ✗
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.
Quick reference
VPN Protocol Comparison
| Protocol | Port | Encryption | Authentication | Use Case |
|---|---|---|---|---|
| IKEv2 / IPsec | UDP 500 / 4500 | AES-256 | Certificates / PSK | Site-to-site & remote access |
| SSL / TLS VPN | TCP 443 | TLS 1.3 | Certificates / MFA | Clientless remote access |
| L2TP / IPsec | UDP 1701 | AES (IPsec) | PSK / Certificates | Legacy remote access |
| WireGuard | UDP 51820 | ChaCha20 | Public keys | Modern high-performance VPN |
| PPTP | TCP 1723 | MPPE (weak) | MS-CHAPv2 | Legacy — avoid in production |
PPTP is considered insecure. IKEv2/IPsec and SSL VPN are the current recommended options.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CISA practice question is part of Courseiva's free ISACA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CISA exam.