CISM Information Security Risk Management Practice Question
Exhibit
Refer to the exhibit. Exhibit: ``` CISCO ASA Firewall Config Snippet access-list INSIDE extended permit tcp 10.0.0.0 255.255.255.0 any eq 443 access-list INSIDE extended permit udp 10.0.0.0 255.255.255.0 any eq 53 access-list OUTSIDE extended deny ip any any ```
Refer to the exhibit. A security analyst reviews the firewall configuration and identifies a potential risk. What is the most likely risk?
⚠ Common exam trap
The trap here is that candidates may focus on the firewall rule allowing outbound DNS traffic and incorrectly assume it only poses a risk of unauthorized external access (option A), overlooking the more subtle but critical risk of data exfiltration via DNS tunneling, which is a well-known covert channel in security assessments.
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
✓
Risk of data exfiltration via DNS tunneling.
The exhibit shows a firewall rule that permits DNS traffic (UDP/TCP port 53) from the internal network to any external destination. This configuration allows internal hosts to perform DNS queries to external servers, which can be exploited for DNS tunneling—a technique where data is encapsulated within DNS queries and responses to bypass security controls and exfiltrate sensitive information. Since DNS traffic is typically allowed through firewalls, this creates a covert channel for data exfiltration, making option D the most likely risk.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Risk of unauthorized external access to internal services.
Why it's wrong here
The ACL permits outgoing traffic, not incoming.
- ✗
Risk of denial-of-service attacks from internal hosts.
Why it's wrong here
DoS would require specific attack vectors, not just outbound rules.
- ✗
Risk of IP spoofing attacks from the inside network.
Why it's wrong here
ACLs do not inherently allow spoofing; spoofing depends on other factors.
- ✓
Risk of data exfiltration via DNS tunneling.
Why this is correct
Permissive DNS outbound can be exploited for covert data transfer.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CISM 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 CISM exam.