CHFI OS and File System Forensics Practice Question
This CHFI practice question tests your understanding of os and file system 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.
During a forensic investigation, an analyst needs to preserve the integrity of evidence on a hard drive. Which of the following is the best practice for acquiring an image of the drive?
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
✓
Use a hardware write blocker and create a bit-stream image.
Option C is correct because using a hardware write blocker ensures that no write commands from the forensic workstation reach the suspect drive, preserving its integrity at the physical level. Creating a bit-stream image (sector-by-sector copy) captures all data, including slack space and unallocated clusters, which is essential for thorough forensic analysis. This combination is the gold standard in digital forensics, as mandated by best practices like those from NIST and the ACPO principles.
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.
✗
Use the 'dd' command to create a raw image without a write blocker.
Why it's wrong here
'dd' can read the drive but does not prevent writes; a write blocker must be used.
✗
Connect the drive to a forensic workstation and use the operating system's copy command.
Why it's wrong here
The OS may write to the drive (e.g., updating timestamps) compromising integrity.
✓
Use a hardware write blocker and create a bit-stream image.
Why this is correct
A write blocker ensures no data is altered on the original drive during acquisition.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Format the drive before imaging to ensure no hidden data is missed.
Why it's wrong here
Formatting destroys data and is never acceptable in forensic acquisition.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that a software-based approach (like dd) is sufficient for imaging, but the trap is that without a hardware write blocker, the forensic workstation's OS may inadvertently write to the suspect drive (e.g., via automount or journaling), compromising evidence integrity.
Detailed technical explanation
How to think about this question
A hardware write blocker operates by intercepting ATA/SCSI commands at the bus level, allowing only read commands (e.g., READ SECTOR) to pass through while blocking write commands (e.g., WRITE SECTOR). A bit-stream image, often created with tools like dd or FTK Imager, produces a forensic image file (e.g., .E01 or .dd) that is an exact duplicate of the source drive at the sector level, including the Master Boot Record, partition tables, and all slack space. In real-world scenarios, failing to use a write blocker has led to evidence being rejected in court, as even a single write operation can alter timestamps or metadata.
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.
OS and File System Forensics — This question tests OS and File System Forensics — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a hardware write blocker and create a bit-stream image. — Option C is correct because using a hardware write blocker ensures that no write commands from the forensic workstation reach the suspect drive, preserving its integrity at the physical level. Creating a bit-stream image (sector-by-sector copy) captures all data, including slack space and unallocated clusters, which is essential for thorough forensic analysis. This combination is the gold standard in digital forensics, as mandated by best practices like those from NIST and the ACPO principles.
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: "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?
Read the scenario before looking for a memorised answer.
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Question Discussion
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