easyMultiple ChoiceObjective-mapped
ISC2 CC Practice Question: Refer to the exhibit
Exhibit
Apr 10 09:15:22 192.168.1.1 %ASA-4-106023: Deny tcp src outside:203.0.113.1/80 dst inside:10.0.0.5/33456 by access-group "INSIDE_IN" [0x0, 0x0]
Refer to the exhibit. A security analyst sees this log entry from a firewall. What is the most likely reason for this denial?
⚠ Common exam trap
ISC2 often tests the concept that a firewall's default implicit deny will drop traffic if no explicit permit exists for the destination port, leading candidates to incorrectly assume the source IP is blacklisted or the packet is malformed.
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 destination port is not allowed
The firewall log entry indicates a packet was denied due to a policy violation, and the most common reason for such a denial in a stateful firewall is that the destination port is not permitted by the configured access control list (ACL) or security policy. Firewalls evaluate traffic against rules that specify allowed source/destination IPs, ports, and protocols; if the destination port is not explicitly allowed, the packet is dropped. This is a standard security practice to restrict unauthorized services.
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 destination port is not allowed
Why this is correct
The access-group denies traffic to the destination port 33456.
- ✗
The source IP is blacklisted
Why it's wrong here
There is no indication the IP is blacklisted.
- ✗
The access-group is misconfigured
Why it's wrong here
The rule explicitly denies this traffic, so configuration is intentional.
- ✗
The packet is malformed
Why it's wrong here
No malformed packet indicators in the log.
Visual reference
Go deeper
Related to this question
Learn chapter
Introduction to Security Principles
Key term
ACL
An Access Control List is a set of rules that determines who or what can access specific network resources or data.
Key term
Access control
Access control is the security practice of determining who or what is allowed to view, use, or enter a resource, and under what conditions.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CC practice question is part of Courseiva's free ISC2 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 CC exam.