The correct choice is to deploy a forward proxy with SSL/TLS inspection because it decrypts outbound encrypted traffic, enabling the detection of malicious C2 payloads hidden within legitimate HTTPS flows on TCP port 443. Without decryption, security tools like an IDS or firewall logs can only see encrypted data, making them blind to the actual content. On the CompTIA SecurityX CAS-004 exam, this scenario tests your understanding of how encrypted traffic inspection fits into a defense-in-depth architecture, often appearing as a trap where candidates mistakenly choose to block all outbound 443 or rely solely on logging. A common memory tip is to remember that “inspection requires decryption”—you cannot inspect what you cannot read. Think of it as a postal inspector who must open a sealed envelope to check for contraband, rather than just logging that a letter was sent.
CAS-004 Security Architecture Practice Question
This CAS-004 practice question tests your understanding of security architecture. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
An incident responder notices that a compromised host is sending encrypted C2 traffic over TCP port 443. The existing firewall rule allows outbound HTTPS (443) to any destination. Which change to the security architecture would best detect this behavior while minimizing impact on legitimate traffic?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deploy a forward proxy with SSL/TLS inspection
An SSL/TLS inspection proxy can decrypt outbound traffic for inspection, allowing detection of malicious content while still allowing legitimate HTTPS. Option A is wrong because blocking all outbound 443 breaks functionality. Option B is wrong because increasing logging does not detect encrypted content. Option D is wrong because IDS cannot inspect encrypted traffic without decryption.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Deploy a forward proxy with SSL/TLS inspection
Why this is correct
A proxy can decrypt, inspect, and re-encrypt traffic to detect malicious payloads.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
Block outbound TCP 443 and require users to use a VPN
Why it's wrong here
This disrupts all HTTPS traffic and may not be feasible.
✗
Enable logging on the firewall for all outbound 443 traffic
Why it's wrong here
Logging alone does not reveal the content of encrypted traffic.
✗
Install a network-based IDS on the internal side of the firewall
Why it's wrong here
An IDS cannot inspect encrypted traffic without decryption keys.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
Security Architecture — This question tests Security Architecture — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Deploy a forward proxy with SSL/TLS inspection — An SSL/TLS inspection proxy can decrypt outbound traffic for inspection, allowing detection of malicious content while still allowing legitimate HTTPS. Option A is wrong because blocking all outbound 443 breaks functionality. Option B is wrong because increasing logging does not detect encrypted content. Option D is wrong because IDS cannot inspect encrypted traffic without decryption.
What should I do if I get this CAS-004 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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