The answer is to disconnect the network cable to isolate the system from the network. This action immediately severs the active C2 connection, halting data exfiltration and remote command injection while preserving the current state of volatile evidence like running processes and network sockets. On the Computer Hacking Forensic Investigator CHFI exam, this scenario tests your understanding of first responder priorities under the order of volatility, where stopping live communication takes precedence over scanning or shutdown. A common trap is choosing to run a forensic tool or power off the system, which either contaminates evidence or destroys memory. Remember the mnemonic “Cable First, Capture Later”—cut the link before you collect the data.
CHFI Incident Response and First Responder Skills Practice Question
This CHFI practice question tests your understanding of incident response and first responder skills. 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.
During incident response, a first responder discovers a compromised system with signs of an active command-and-control (C2) connection. What is the MOST important immediate action to preserve evidence and prevent further damage?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
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
✓
Disconnect the network cable to isolate the system from the network.
Option B is correct because disconnecting the network cable immediately stops the active C2 communication, preventing further data exfiltration and command injection while preserving the current state of memory and disk. This action maintains the integrity of volatile evidence (e.g., network connections, running processes) and avoids the data loss that would occur with a shutdown or the evidence contamination that would result from running a scan.
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.
✗
Create a full disk image before taking any other action.
Why it's wrong here
Imaging is important but should be done after isolating the system to prevent tampering during the imaging process.
✓
Disconnect the network cable to isolate the system from the network.
Why this is correct
Disconnecting the network cable stops C2 communication, preserves volatile data, and allows for a controlled forensic acquisition.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Immediately shut down the system to prevent further data exfiltration.
Why it's wrong here
Shutting down destroys volatile data (RAM, network connections) that may contain critical evidence.
✗
Run a full antivirus scan to remove the malware.
Why it's wrong here
Antivirus scans modify file timestamps and may delete malicious files, destroying evidence.
Common exam traps
Common exam trap: answer the scenario, not the keyword
EC-Council often tests the misconception that a full disk image is always the first priority, but in an active C2 scenario, network isolation must come first to prevent ongoing damage and preserve volatile evidence.
Detailed technical explanation
How to think about this question
When a C2 connection is active, the system’s network stack maintains TCP sessions with remote IPs and ports (e.g., using ephemeral ports). Disconnecting the network cable (layer 1 isolation) causes an immediate TCP RST or timeout, freezing the state of network artifacts in memory and disk (e.g., netstat output, firewall logs). In real-world scenarios, attackers often use encrypted C2 channels (e.g., HTTPS over port 443) or DNS tunneling, so a live response with tools like Wireshark or Volatility can capture the encryption keys or session data before isolation is broken.
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 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CHFI question in full detail.
Incident Response and First Responder Skills — This question tests Incident Response and First Responder Skills — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Disconnect the network cable to isolate the system from the network. — Option B is correct because disconnecting the network cable immediately stops the active C2 communication, preventing further data exfiltration and command injection while preserving the current state of memory and disk. This action maintains the integrity of volatile evidence (e.g., network connections, running processes) and avoids the data loss that would occur with a shutdown or the evidence contamination that would result from running a scan.
What should I do if I get this CHFI 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: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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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