The answer is that the firewall denied the traffic from 10.0.1.15 to 10.0.2.10. This is correct because the firewall’s access control list (ACL) processes rules sequentially, and the first matching rule for this traffic is a deny action that explicitly blocks the source IP 10.0.1.15. In sequential processing, once a deny rule matches, the packet is dropped immediately without evaluating any subsequent rules, even if later rules would permit the traffic. On the ISC2 Certified in Cybersecurity CC exam, this concept tests your understanding of ACL order of operations and how a firewall applies a deny action as the decisive factor. A common trap is assuming that a permit rule later in the list overrides an earlier deny, but sequential processing means the first match wins. Remember the memory tip: “First match, final action”—the rule that matches first determines the packet’s fate, so a deny early in the list blocks all matching traffic regardless of later permits.
ISC2 CC Security Principles Practice Question
This CC practice question tests your understanding of security principles. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
syslog: 2025-03-15T10:23:45Z FW01 %SEC-6-IPACCESSLOGP: list 101 denied tcp 10.0.1.15(54321) -> 10.0.2.10(23), 1 packet
Refer to the exhibit. What action did the firewall take on the traffic from 10.0.1.15 to 10.0.2.10?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Denied the traffic
The firewall denied the traffic from 10.0.1.15 to 10.0.2.10 because the access control list (ACL) or security policy explicitly denies the source IP 10.0.1.15, as shown in the exhibit. The firewall processes rules sequentially, and the first matching rule for this traffic is a deny entry, so the packet is dropped without further inspection or logging unless specified.
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.
✗
Logged and permitted
Why it's wrong here
The log indicates the packet was denied, not permitted.
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the sequential processing of ACLs, where candidates mistakenly think a later permit rule overrides an earlier deny rule, but the first match always wins.
Detailed technical explanation
How to think about this question
Cisco firewalls (e.g., ASA, FTD) use ordered ACLs where the first match determines the action; a deny rule stops all further processing, including NAT and inspection. In real-world scenarios, misplacing a deny rule before a permit rule can silently block legitimate traffic, often leading to troubleshooting challenges where packet captures show the traffic reaching the firewall but not exiting.
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 analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CC question in full detail.
Security Principles — This question tests Security Principles — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Denied the traffic — The firewall denied the traffic from 10.0.1.15 to 10.0.2.10 because the access control list (ACL) or security policy explicitly denies the source IP 10.0.1.15, as shown in the exhibit. The firewall processes rules sequentially, and the first matching rule for this traffic is a deny entry, so the packet is dropped without further inspection or logging unless specified.
What should I do if I get this CC 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
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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. A network administrator configures the ACL on a router as shown. What is the effect of this access list?
easy
✓ A.Blocks Telnet traffic entering the interface, but allows all other traffic
B.Blocks SSH traffic (port 22) from entering the interface
C.Blocks Telnet traffic leaving the interface, but allows all other traffic
D.Blocks all TCP traffic except Telnet
Why A: Option A is correct because the ACL denies TCP traffic to port 23 (Telnet) and permits all other IP traffic. Option B is wrong because SSH is port 22. Option C is wrong because the ACL is applied inbound on Gig0/1, so it filters incoming traffic only, not outgoing. Option D is wrong because it applies to all TCP traffic, not just Telnet.
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Question Discussion
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