The correct first step is to use EDR to identify the process or service generating the outbound connections on the web server. This approach directly addresses the core challenge of a SOC investigation into unusual outbound traffic: without knowing which process is initiating the encrypted connections, you cannot determine if it’s a legitimate application update or a hidden backdoor. EDR telemetry provides process-level visibility, allowing you to trace the HTTPS traffic back to its executable, parent process, and command-line arguments, which is essential for scoping the compromise before any containment actions. On the CompTIA SecurityX CAS-004 exam, this scenario tests your ability to prioritize investigative steps over reactive controls—a common trap is jumping to block the firewall rule or isolate the host, which can destroy forensic evidence and disrupt legitimate services. Remember the memory tip: “Process before perimeter”—always identify the source process with EDR before altering network controls.
CAS-004 Security Architecture Practice Question
This CAS-004 practice question tests your understanding of security architecture. 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 SOC analyst discovers unusual outbound traffic from a host in the production DMZ to an unknown IP address on the internet. The traffic consists of encrypted connections (HTTPS) to a domain that was registered three days ago. The host is a web server that has been fully patched and is configured with a default deny egress firewall policy, but this particular traffic is being allowed because a recently added rule permits outbound HTTPS to any destination for a specific application's updates. The security architect is called in to investigate and must determine the best course of action to identify the scope of the potential compromise and prevent further data exfiltration. The architect has access to network flow data, endpoint detection and response (EDR) telemetry, and firewall logs. What should the security architect do FIRST?
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.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use EDR to identify the process or service generating the outbound connections on the web server.
Option C (Check EDR telemetry on the host to identify the process making the outbound connections) is the best first step because it provides visibility into the exact source of the traffic. Option A (Block the outbound HTTPS rule immediately) may disrupt legitimate traffic and does not help identify the scope. Option B (Enable full SSL inspection on the firewall) is resource-intensive and can be deployed later. Option D (Isolate the host from the network) is a containment step but should follow identification to ensure proper forensic collection.
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.
✗
Enable full SSL inspection on the firewall to decrypt the traffic and analyze the contents.
Why it's wrong here
SSL inspection is heavy and may not be immediately feasible; also, it might alert the attacker.
✓
Use EDR to identify the process or service generating the outbound connections on the web server.
Why this is correct
EDR can pinpoint the root cause (e.g., a webshell or backdoor) for further investigation.
Clue confirmation
The clue words "best", "first" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
Isolate the web server from the network to prevent further data exfiltration.
Why it's wrong here
Isolation is a strong containment step but should be done after gathering initial evidence to preserve forensic data.
✗
Immediately remove the outbound HTTPS rule to block the traffic.
Why it's wrong here
This may disrupt legitimate application updates and does not provide forensic insight.
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: Use EDR to identify the process or service generating the outbound connections on the web server. — Option C (Check EDR telemetry on the host to identify the process making the outbound connections) is the best first step because it provides visibility into the exact source of the traffic. Option A (Block the outbound HTTPS rule immediately) may disrupt legitimate traffic and does not help identify the scope. Option B (Enable full SSL inspection on the firewall) is resource-intensive and can be deployed later. Option D (Isolate the host from the network) is a containment step but should follow identification to ensure proper forensic collection.
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", "first". 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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