The answer is fileless malware that only resided in memory. This is the most likely explanation because fileless malware operates entirely within RAM, never writing its payload to disk, which accounts for the clean disk image and antivirus logs despite active C2 traffic over HTTPS. On the Computer Hacking Forensic Investigator CHFI exam, this scenario tests your understanding of memory forensics versus traditional disk forensics—a common trap is assuming that a clean disk means a clean system, when in fact the malware may be hiding in volatile memory. To detect such threats, you must analyze RAM dumps, process lists, and network connections rather than relying on file-based scans. A helpful memory tip: “No file on disk, but traffic on the wire—think memory-resident malware.”
CHFI Network and Cloud Forensics Practice Question
This CHFI practice question tests your understanding of network and cloud forensics. 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.
You are investigating a network breach at a financial institution. The organization uses a network-based intrusion detection system (NIDS) and maintains full packet capture (PCAP) for critical segments. The incident allegedly started with a spear-phishing email that delivered a remote access trojan (RAT). The security team has isolated the infected host and provided you with a disk image of the host and a PCAP file covering the network traffic from the host for the 24-hour period before isolation. In the PCAP, you see a series of TCP connections from the host to an external IP address on port 443 (HTTPS). The external IP is known to be associated with a command-and-control (C2) server. However, the disk image shows no evidence of the RAT binary or any malicious files. The host's antivirus logs are clean. Which of the following is the most likely explanation for the lack of evidence on the disk?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The malware was fileless and only resided in memory
The absence of the RAT binary and any malicious files on the disk, combined with clean antivirus logs and active C2 traffic over HTTPS, strongly indicates a fileless malware infection. Fileless malware operates entirely in memory (RAM), never writing its payload to disk, which explains why the disk image shows no artifacts and why traditional file-scanning antivirus did not detect it. The TCP connections to the C2 server on port 443 are consistent with a memory-resident RAT that loads directly into a legitimate process (e.g., PowerShell, WMI, or a script interpreter) and communicates over encrypted HTTPS to evade network inspection.
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 antivirus software deleted the malicious files before the image was taken
Why it's wrong here
Antivirus logs would show deletion events.
✗
The hard drive was reimaged before the forensic image was taken
Why it's wrong here
The image was taken after isolation, so reimaging would have destroyed evidence.
✗
The RAT uses a rootkit to hide its files
Why it's wrong here
A rootkit hides files but they still exist; forensic tools can often detect hidden files.
✓
The malware was fileless and only resided in memory
Why this is correct
Fileless malware leaves no persistent artifacts on disk.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
EC-Council often tests the distinction between file-based and fileless malware, and the trap here is assuming that a rootkit (Option C) is the only way to hide files, when in fact fileless malware never writes files to disk at all, making rootkits unnecessary for evasion.
Trap categories for this question
Command / output trap
Antivirus logs would show deletion events.
Detailed technical explanation
How to think about this question
Fileless malware often leverages living-off-the-land binaries (LOLBins) such as PowerShell, certutil, or mshta to execute payloads directly in memory without touching disk. The C2 traffic over HTTPS (port 443) is particularly insidious because it blends with legitimate encrypted web traffic, making it difficult for NIDS to detect malicious commands without decrypting the session. In real-world incidents, memory forensics tools like Volatility can recover the RAT code from process memory dumps, even when disk forensics yields nothing.
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.
Network and Cloud Forensics — This question tests Network and Cloud Forensics — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The malware was fileless and only resided in memory — The absence of the RAT binary and any malicious files on the disk, combined with clean antivirus logs and active C2 traffic over HTTPS, strongly indicates a fileless malware infection. Fileless malware operates entirely in memory (RAM), never writing its payload to disk, which explains why the disk image shows no artifacts and why traditional file-scanning antivirus did not detect it. The TCP connections to the C2 server on port 443 are consistent with a memory-resident RAT that loads directly into a legitimate process (e.g., PowerShell, WMI, or a script interpreter) and communicates over encrypted HTTPS to evade network inspection.
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: "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.
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Question Discussion
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