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.
An investigator creates a forensic image using dcfldd with the following command: dcfldd if=/dev/sdb of=image.dd hash=sha256 hashwindow=10M hashlog=hash.txt. What is the effect of the 'hashwindow=10M' parameter?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It divides the output into 10 MB chunks and hashes each chunk, logging the results
Option A is correct because the `hashwindow=10M` parameter in dcfldd instructs the tool to compute a SHA-256 hash for every 10 MB segment (window) of the input data as it is being copied, and then log each segment's hash to the specified hashlog file. This allows the investigator to verify the integrity of individual chunks of the forensic image, which is useful for detecting corruption or tampering in specific regions of the image without rehashing the entire file.
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.
✓
It divides the output into 10 MB chunks and hashes each chunk, logging the results
Why this is correct
This is the correct behavior; it enables piecewise verification.
Related concept
Read the scenario before looking for a memorised answer.
✗
It sets the input buffer size to 10 MB for performance
Why it's wrong here
Buffer size is controlled by bs, not hashwindow.
✗
It verifies the hash of the input device in 10 MB windows before copying
Why it's wrong here
hashwindow applies to the output, not input verification.
✗
It causes the tool to hash the entire image only after completion
Why it's wrong here
hashwindow creates per-block hashes during acquisition, not just an overall hash.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between 'hashing during acquisition' and 'hashing after completion' — the trap here is that candidates may assume `hashwindow` is for performance tuning (buffer size) or for pre-copy verification, rather than understanding it as a segmentation feature for incremental hashing and logging.
Trap categories for this question
Command / output trap
hashwindow applies to the output, not input verification.
Detailed technical explanation
How to think about this question
Under the hood, dcfldd uses a rolling hash approach where the input stream is divided into fixed-size windows (10 MB in this case), and a SHA-256 hash is computed for each window independently. This is particularly valuable in forensic imaging of large drives (e.g., 1 TB) because if a later verification fails, the investigator can pinpoint which 10 MB segment is corrupt, avoiding the need to reacquire the entire drive. The hashlog file stores each window's hash sequentially, enabling granular integrity checks without reprocessing the whole image.
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: It divides the output into 10 MB chunks and hashes each chunk, logging the results — Option A is correct because the `hashwindow=10M` parameter in dcfldd instructs the tool to compute a SHA-256 hash for every 10 MB segment (window) of the input data as it is being copied, and then log each segment's hash to the specified hashlog file. This allows the investigator to verify the integrity of individual chunks of the forensic image, which is useful for detecting corruption or tampering in specific regions of the image without rehashing the entire file.
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.
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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