The correct answer is that the primary reason for using a hardware write-blocker is to ensure the operating system does not mount the drive as writable. This is achieved by physically intercepting the SATA or IDE bus between the suspect drive and the forensic workstation, allowing only read commands like ATA READ DMA to pass through while blocking write commands such as ATA WRITE DMA. Without this hardware-level intervention, the OS would automatically write to the drive—updating timestamps, journaling, or creating prefetch files—thereby altering evidence and breaking the chain of custody. On the CHFI exam, this question tests your understanding of evidence integrity at the hardware layer, often appearing as a trap where candidates mistakenly choose “prevent accidental deletion” instead of the OS mounting issue. Remember the memory tip: “Hardware blocks writes, OS never mounts.”
CHFI Computer Forensics Fundamentals and Process Practice Question
This CHFI practice question tests your understanding of computer forensics fundamentals and process. 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 acquires a hard drive using a hardware write blocker. Which of the following is the PRIMARY reason for using a hardware write blocker?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
To ensure that the operating system does not mount the drive as writable.
The primary reason for using a hardware write blocker is to physically intercept the SATA/IDE bus between the suspect drive and the forensic workstation, ensuring that only read commands (e.g., ATA READ DMA) are passed through while blocking any write commands (e.g., ATA WRITE DMA). This prevents the operating system from mounting the drive as writable, which would otherwise cause automatic writes (e.g., timestamp updates, journaling, or prefetch creation) that alter evidence and break the chain of custody.
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.
✗
To increase the transfer speed of the imaging process.
Why it's wrong here
Write blockers do not increase speed; they may even slow it slightly.
✗
To bypass the drive's password protection.
Why it's wrong here
Write blockers do not bypass passwords.
✗
To compress the data during imaging.
Why it's wrong here
Compression is a separate function, not provided by write blockers.
✓
To ensure that the operating system does not mount the drive as writable.
Why this is correct
The primary purpose is to prevent any writes to the original evidence drive.
Clue confirmation
The clue word "primary" 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
The trap here is that candidates confuse the write blocker's purpose with performance features (speed, compression) or assume it can bypass security mechanisms, when in fact its sole forensic function is to guarantee read-only access at the hardware interface level.
Detailed technical explanation
How to think about this question
Under the hood, a hardware write blocker implements a bridge that inspects each ATA/SCSI command packet; if the command opcode is a write (e.g., 0x30 for WRITE SECTORS), the blocker either drops the command or returns an error, while read commands (e.g., 0x20 for READ SECTORS) are forwarded transparently. In a real-world scenario, if a drive is connected directly to a forensic workstation running Windows 10, the OS will automatically write volume mount points, restore points, and $LogFile updates to the drive, corrupting evidence—the write blocker prevents all such writes at the hardware level.
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 practitioner preparing for the CHFI exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CHFI question in full detail.
Computer Forensics Fundamentals and Process — This question tests Computer Forensics Fundamentals and Process — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: To ensure that the operating system does not mount the drive as writable. — The primary reason for using a hardware write blocker is to physically intercept the SATA/IDE bus between the suspect drive and the forensic workstation, ensuring that only read commands (e.g., ATA READ DMA) are passed through while blocking any write commands (e.g., ATA WRITE DMA). This prevents the operating system from mounting the drive as writable, which would otherwise cause automatic writes (e.g., timestamp updates, journaling, or prefetch creation) that alter evidence and break the chain of custody.
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: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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