The answer is that permitting all HTTPS and DNS traffic from any internet source to a critical server is the most significant risk because it directly increases the attack surface. By allowing broad inbound access on TCP/443 and UDP/53 without restricting source IPs, the firewall ACL exposes the server to exploitation of vulnerabilities in web server software and DNS services, such as SQL injection, cross-site scripting, or DNS tunneling. On the CRISC exam, this scenario tests your ability to identify how overly permissive ACLs expand the attack surface, a core concept in risk identification and control design. A common trap is focusing on the protocol itself as safe, rather than recognizing that unrestricted access to common services invites attack. Remember the memory tip: “Permit all, risk fall”—any ACL that says “permit any” for high-risk ports like 443 or 53 is a red flag for increased attack surface.
CRISC Risk Response and Mitigation Practice Question
This CRISC practice question tests your understanding of risk response and mitigation. 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.
Exhibit
Refer to the exhibit.
Access List: ACL-01
10 deny ip host 10.1.1.10 any
20 permit tcp 10.1.1.0 0.0.0.255 any eq 443
30 permit udp 10.1.1.0 0.0.0.255 any eq 53
40 deny ip any any
Refer to the exhibit. A risk practitioner is reviewing the access control list for a critical server. The ACL is applied inbound on the interface connecting to the internet. Which of the following is the MOST significant risk?
Refer to the exhibit.
Access List: ACL-01
10 deny ip host 10.1.1.10 any
20 permit tcp 10.1.1.0 0.0.0.255 any eq 443
30 permit udp 10.1.1.0 0.0.0.255 any eq 53
40 deny ip any any
A
The ACL permits all HTTPS and DNS traffic from the subnet, increasing attack surface
Broad permits may allow unauthorized traffic.
B
The ACL has no logging enabled
Why wrong: Lack of logging is a concern but less critical than broad permits.
C
The ACL is missing a permit statement for HTTP
Why wrong: HTTP is not required; HTTPS is more secure.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The ACL permits all HTTPS and DNS traffic from the subnet, increasing attack surface
Option A is correct because permitting all HTTPS (TCP/443) and DNS (UDP/53) traffic from any source on the internet to the critical server unnecessarily exposes the server to potential exploitation of vulnerabilities in the web server software (e.g., Apache, Nginx) and DNS resolver services. This broad permit statement increases the attack surface significantly, as HTTPS and DNS are common vectors for attacks such as SQL injection, cross-site scripting, and DNS amplification or tunneling. The risk is heightened because the ACL is applied inbound on the internet-facing interface, meaning all external traffic matching these protocols is allowed without restriction, bypassing any stateful inspection or application-layer filtering.
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 ACL permits all HTTPS and DNS traffic from the subnet, increasing attack surface
Why this is correct
Broad permits may allow unauthorized traffic.
Related concept
Read the scenario before looking for a memorised answer.
✗
The ACL has no logging enabled
Why it's wrong here
Lack of logging is a concern but less critical than broad permits.
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often focus on missing logging (option B) or missing HTTP (option C) as the most critical issue, but the real risk is the overly permissive ACL that allows all HTTPS and DNS traffic from any source, which dramatically increases the attack surface and is a classic misconfiguration in ACL design.
Detailed technical explanation
How to think about this question
In Cisco ACLs, the implicit deny all at the end of the list blocks any traffic not explicitly permitted, so missing a permit statement for HTTP (option C) would simply block HTTP traffic, which is often desirable for a critical server that should only be accessed via HTTPS. However, permitting all HTTPS and DNS traffic from any source (option A) means the ACL does not restrict source IP addresses, allowing any external host to attempt connections to the server’s HTTPS service and DNS resolver, which could be exploited via vulnerabilities like CVE-2023-44487 (HTTP/2 rapid reset) or DNS cache poisoning. The ACL is applied inbound on the internet-facing interface, so it filters traffic before it reaches the server, but without additional controls like a firewall or IPS, the broad permit statements create a direct path for attackers.
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 administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
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.
Risk Response and Mitigation — This question tests Risk Response and Mitigation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The ACL permits all HTTPS and DNS traffic from the subnet, increasing attack surface — Option A is correct because permitting all HTTPS (TCP/443) and DNS (UDP/53) traffic from any source on the internet to the critical server unnecessarily exposes the server to potential exploitation of vulnerabilities in the web server software (e.g., Apache, Nginx) and DNS resolver services. This broad permit statement increases the attack surface significantly, as HTTPS and DNS are common vectors for attacks such as SQL injection, cross-site scripting, and DNS amplification or tunneling. The risk is heightened because the ACL is applied inbound on the internet-facing interface, meaning all external traffic matching these protocols is allowed without restriction, bypassing any stateful inspection or application-layer filtering.
What should I do if I get this CRISC 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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Refer to the exhibit. An organization uses this firewall access list. What is the MOST significant risk associated with this configuration?
medium
A.The final rule denies all traffic
B.HTTPS traffic is permitted to any destination
C.SSH access is only allowed from internal network
✓ D.HTTP traffic is permitted from any source to any destination
Why D: Option D is correct because the rule permit tcp any any eq 80 allows unrestricted HTTP access from any source, increasing exposure to web attacks. Option A is wrong because SSH is restricted to internal network. Option B is wrong because HTTPS is needed for web traffic. Option C is wrong because the deny all rule is proper.
Last reviewed: Jun 11, 2026
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This CRISC 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 CRISC exam.
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