CS0-003 Incident Response and Management Practice Question
During a forensic investigation, an analyst creates a disk image using dd with a SHA256 hash. Later, the analyst needs to verify the integrity of the image before analysis. Which command should the analyst use to compare the original hash with a newly computed hash?
⚠ Common exam trap
CS0-004 often tests command syntax and hash algorithm matching — candidates pick md5sum out of habit or choose a non-existent command like 'chksum -a sha256', forgetting that the hash algorithm must match the original baseline exactly.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
sha256sum image.dd
The analyst needs to recompute the SHA256 hash of the image file and compare it to the original value. The command 'sha256sum image.dd' computes the SHA256 digest of the file directly, which is the standard Linux utility for this purpose and produces output that can be diffed against the original hash.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
md5sum original.dd
Why it's wrong here
Running md5sum computes an MD5 digest, but the original evidence hash was generated with SHA256, and comparing digests from two different hash algorithms is meaningless since they produce entirely different fixed-length outputs even for identical input; the verification hash must use the same algorithm, SHA256, as the original to yield a comparable result.
- ✗
dd if=image.dd | sha256sum
Why it's wrong here
Piping dd's output into sha256sum unnecessarily re-reads and streams the entire image through an extra process layer just to compute a hash that sha256sum could calculate directly from the file, adding overhead and potential points of failure such as a broken pipe, without providing any advantage over hashing the file directly.
- ✓
sha256sum image.dd
Why this is correct
Running sha256sum directly against the image file recomputes its SHA256 digest using the same algorithm and tool convention as the original acquisition hash, producing a value the analyst can directly diff against the recorded original hash to confirm bit-for-bit integrity and an unbroken chain of custody before proceeding with analysis.
- ✗
chksum -a sha256 image.dd
Why it's wrong here
chksum is not a standard utility on Linux systems; the correct dedicated command for computing a SHA256 digest is sha256sum (or shasum -a 256 on some distributions), so this command would simply fail with a command-not-found error rather than produce any hash for comparison.
Go deeper
Related to this question
Learn chapter
Digital Forensic Evidence Collection
Key term
Analysis
In incident response, analysis is the process of examining data and events to determine what happened, how it happened, and what actions to take.
Key term
Disk image
A disk image is a sector-by-sector copy of an entire storage device, such as a hard drive or SSD, used in incident response to preserve forensic evidence exactly as it existed at a point in time.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
This CS0-004 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CS0-004 exam.