The answer is to implement a firewall rule that denies traffic from the internal host to the external IP address. This rule is correct because it uses both the source and destination parameters to create a precise match, blocking only the specific traffic flow to the command-and-control server while leaving all other traffic unaffected. This approach directly applies the principle of least privilege in firewall rule design, ensuring minimal disruption to network operations. On the Systems Security Certified Practitioner SSCP exam, this scenario tests your understanding of granular access control and the importance of specificity in rule creation, often appearing as a trap where broader deny rules (like blocking all traffic to the external IP) are tempting but incorrect. A useful memory tip is "source-destination specificity"—always pair the exact source with the exact destination to avoid over-blocking.
SSCP Network and Communications Security Practice Question
This SSCP practice question tests your understanding of network and communications security. 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.
A security analyst discovers that an internal host is sending traffic to an external IP address known to be a command-and-control server. The analyst wants to block only that specific traffic without affecting other traffic. Which firewall rule should be implemented?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deny traffic from the internal host to the external IP.
Option D is correct because it creates a specific deny rule that matches only the source IP of the internal host and the destination IP of the command-and-control server, blocking that exact traffic flow while allowing all other traffic to and from both hosts. This is the most precise and least disruptive approach, adhering to the principle of least privilege in firewall rule design.
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.
✗
Deny all traffic from the internal host.
Why it's wrong here
This would block all communication from the host.
✗
Deny all traffic to the external IP.
Why it's wrong here
This would block all systems from accessing that IP.
✗
Deny traffic on the specific port used.
Why it's wrong here
This would block that port for all traffic, potentially affecting legitimate communication.
✓
Deny traffic from the internal host to the external IP.
Why this is correct
This provides a targeted block without affecting other traffic.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose a broad deny rule (like denying all traffic to the external IP) because they focus on the malicious destination, forgetting that such a rule would block all traffic to that IP from any source, potentially impacting other hosts or services.
Detailed technical explanation
How to think about this question
In stateful firewall implementations, such as those using iptables or pf, a rule like 'deny from internal host to external IP' is evaluated as a 5-tuple match (source IP, destination IP, source port, destination port, protocol). This granularity ensures that only the specific session is blocked, while other sessions from the same host or to the same IP remain unaffected. In a real-world scenario, this approach is critical when the internal host is a multi-purpose server that must continue serving other external services.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network and Communications Security — This question tests Network and Communications Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Deny traffic from the internal host to the external IP. — Option D is correct because it creates a specific deny rule that matches only the source IP of the internal host and the destination IP of the command-and-control server, blocking that exact traffic flow while allowing all other traffic to and from both hosts. This is the most precise and least disruptive approach, adhering to the principle of least privilege in firewall rule design.
What should I do if I get this SSCP 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.
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Question Discussion
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