- A
The firewall has an explicit permit rule for traffic from DMZ to Inside on any destination.
An explicit rule would override the default deny and allow the attack traffic.
- B
The firewall was configured in transparent mode, allowing all traffic.
Why wrong: Transparent mode acts as a layer 2 bridge, but rules still apply; would not explain selective allowance.
- C
The attacker used a VPN connection that bypassed the firewall.
Why wrong: No indication of VPN; the firewall logs showed the attack originated from DMZ IP.
- D
The firewall's default behavior permits traffic from lower security level to higher if the connection is initiated from the higher level.
Why wrong: Default behavior for lower-to-higher is deny; only return traffic for existing sessions is allowed.
Quick Answer
The answer is an explicit permit rule for traffic from DMZ to Inside on any destination. This is correct because Cisco ASA firewalls enforce a default deny behavior for traffic moving from a lower security level (like the DMZ, typically level 50) to a higher security level (like the Inside, typically level 100). Without an explicit permit statement, the firewall would automatically block any such traffic, so the attacker’s pivot from the compromised web server to the internal database server could only succeed if an administrator had configured a rule allowing DMZ-to-Inside traffic. On the ISC2 Certified in Cybersecurity CC exam, this scenario tests your understanding of the Cisco ASA security levels and default deny principle, often appearing as a trap where test-takers overlook the fact that default behavior is overridden only by explicit permits. A key memory tip: “Lower to higher is denied by default; if it flows, a rule must be the cause.”
ISC2 CC Network Security Practice Question
This CC practice question tests your understanding of network security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
A medium-sized enterprise uses a Cisco ASA firewall configured with multiple security zones (Inside, Outside, DMZ). The DMZ hosts a web server that must be accessible from the Internet on TCP 443. The Inside network (10.0.0.0/24) hosts internal clients. The web server has IP 172.16.0.10. The firewall's current rules: allow any from Outside to DMZ on TCP 443; allow any from Inside to Outside; deny all else. Recently, the security team noticed that an attacker compromised the web server and used it to launch an attack against an internal database server at 10.0.0.50. The attack was successful because the firewall allowed traffic from the DMZ to the Inside. The firewall's default behavior is to deny traffic from lower security zones to higher security zones (DMZ is lower than Inside). What is the MOST likely reason this traffic was allowed?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 firewall has an explicit permit rule for traffic from DMZ to Inside on any destination.
The correct answer is A because the firewall's default behavior is to deny traffic from a lower security zone (DMZ) to a higher security zone (Inside). For the attack to succeed, an explicit permit rule must have been configured to allow traffic from DMZ to Inside. The existing rules only permit Outside to DMZ on TCP 443 and Inside to Outside; without an explicit DMZ-to-Inside rule, the default deny would have blocked the attack. Thus, the most likely reason is that an administrator inadvertently or intentionally added such a permit rule.
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 firewall has an explicit permit rule for traffic from DMZ to Inside on any destination.
Why this is correct
An explicit rule would override the default deny and allow the attack traffic.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The firewall was configured in transparent mode, allowing all traffic.
Why it's wrong here
Transparent mode acts as a layer 2 bridge, but rules still apply; would not explain selective allowance.
- ✗
The attacker used a VPN connection that bypassed the firewall.
- ✗
The firewall's default behavior permits traffic from lower security level to higher if the connection is initiated from the higher level.
Why it's wrong here
Default behavior for lower-to-higher is deny; only return traffic for existing sessions is allowed.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the misconception that the ASA's default behavior allows traffic from lower to higher security levels if the connection is initiated from the higher level, but in reality, the ASA only permits return traffic for established connections; new connections from lower to higher are always denied by default.
Trap categories for this question
Command / output trap
No indication of VPN; the firewall logs showed the attack originated from DMZ IP.
Detailed technical explanation
How to think about this question
Cisco ASA uses security levels (0-100) where higher levels are more trusted. By default, traffic from a higher security level to a lower level is allowed, but traffic from lower to higher is denied unless an ACL explicitly permits it. This is enforced by the ASA's stateful inspection engine, which checks the security level of the ingress interface against the egress interface. In this scenario, DMZ (typically level 50) is lower than Inside (level 100), so the default deny would block the attack. The fact that the attack succeeded indicates an explicit permit rule was present, likely misconfigured during troubleshooting or a poorly scoped 'allow any' rule.
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.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this CC question test?
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The firewall has an explicit permit rule for traffic from DMZ to Inside on any destination. — The correct answer is A because the firewall's default behavior is to deny traffic from a lower security zone (DMZ) to a higher security zone (Inside). For the attack to succeed, an explicit permit rule must have been configured to allow traffic from DMZ to Inside. The existing rules only permit Outside to DMZ on TCP 443 and Inside to Outside; without an explicit DMZ-to-Inside rule, the default deny would have blocked the attack. Thus, the most likely reason is that an administrator inadvertently or intentionally added such a permit rule.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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Last reviewed: Jun 30, 2026
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.
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