Forensic Acquisition Best Practices — Hardware Write Blocker and EWF Imaging
You are a forensic investigator responding to a security incident at a medium-sized company. The incident involved an attacker gaining unauthorized access to a Windows Server 2019 system. The server was taken offline by the IT team immediately after detection. Your task is to acquire forensic evidence from the server's hard drive. The server has a single 500 GB NTFS partition. You have a forensic workstation with a write blocker, a SATA-to-USB adapter, and a forensic imaging tool that supports both dd and EWF (E01) formats. The server is still physically in the server room, and the IT team has powered it off. You need to create a forensic image that preserves the integrity of the evidence and allows for efficient analysis. Which of the following is the most appropriate course of action?
Quick Answer
The answer is to remove the hard drive, connect it via a write blocker to the forensic workstation, and create an EWF (E01) image stored locally. This is correct because forensic acquisition best practices demand hardware write-blocking to prevent any alteration of the source drive during imaging, while the EWF (E01) format provides built-in compression, metadata, and integrity checks like CRC32 and MD5, which are critical for preserving evidence and enabling efficient analysis. On the CHFI exam, this scenario tests your understanding of proper acquisition methodology—specifically that live imaging or network transfers introduce risks of data corruption or tampering. A common trap is choosing dd over E01, but E01’s compression and validation features make it superior for long-term case management. Memory tip: “Block before you copy, E01 for the win.”
⚠ Common exam trap
EC-Council often tests the misconception that using a forensic live CD is sufficient for write protection, but without a hardware write blocker, the OS may still write to the drive (e.g., via journaling or mount operations), compromising evidence integrity.
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
✓
Remove the hard drive, connect it via a write blocker to the forensic workstation, and create an EWF (E01) image stored locally on the forensic workstation's internal drive.
It follows best practices for forensic acquisition: removing the hard drive and connecting it via a write blocker ensures that no data is altered during imaging. Using EWF (E01) format provides compression, metadata, and integrity checks (e.g., CRC32, MD5, SHA-1), which are essential for efficient analysis and evidence preservation. Storing the image locally on the forensic workstation avoids network latency and potential data corruption.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Boot the server using a forensic live CD, connect an external USB drive to the server, and use 'dd' to create a raw image on the external drive.
Why it's wrong here
Booting from live CD may write to the system and the dd command does not use a write blocker; also, live acquisition is riskier.
- ✗
Use the server's built-in backup utility to create a system state backup and copy it to a network share.
Why it's wrong here
Backup utilities do not create a bit-for-bit forensic image and may miss deleted data; network transfer risks integrity.
- ✗
Remove the hard drive, connect it via a write blocker to the forensic workstation, and then use 'dd' over a network connection to send the image to a remote server.
Why it's wrong here
Imaging over the network is not recommended due to potential data corruption and slower speeds; local imaging is preferred.
- ✓
Remove the hard drive, connect it via a write blocker to the forensic workstation, and create an EWF (E01) image stored locally on the forensic workstation's internal drive.
Why this is correct
This method uses a write blocker to preserve integrity, and EWF format provides compression and metadata for efficient analysis.
Go deeper
Related to this question
Learn chapter
Evidence Handling and Chain of Custody
Key term
EnCase Forensic
EnCase Forensic is a digital forensics software suite used by investigators to acquire, analyze, and report on data from computers and mobile devices in a legally admissible way.
Key term
Disk Imaging
Disk imaging is the process of creating an exact, bit-for-bit copy of a storage drive, preserving all data, deleted files, and unallocated space for forensic analysis or system recovery.
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Same concept, more angles
2 more ways this is tested on CHFI
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Match each forensic acquisition method to its description.
medium- ✓ A.Live Acquisition: Acquisition performed on a running system to capture volatile data.
- ✓ B.Dead Acquisition: Acquisition performed on a powered-off system to capture non-volatile data.
- ✓ C.Logical Acquisition: Acquisition that captures files and folder structure without unallocated space.
- ✓ D.Physical Acquisition: Acquisition that captures the entire storage device bit-by-bit, including unallocated space.
- E.Live Acquisition: Acquisition that captures only the files and folders.
- F.Dead Acquisition: Acquisition performed on a running system.
Why A: Live acquisition captures volatile data from a running system, dead acquisition captures non-volatile data from a powered-off system, logical acquisition captures file structure only, and physical acquisition captures the entire device. Common confusions include swapping live and dead, or logical and physical.
Variation 2. 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?
easy- A.Use the 'dd' command to create a raw image without a write blocker.
- B.Connect the drive to a forensic workstation and use the operating system's copy command.
- ✓ C.Use a hardware write blocker and create a bit-stream image.
- D.Format the drive before imaging to ensure no hidden data is missed.
Why C: 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.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CHFI practice question is part of Courseiva's free EC-Council 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 CHFI exam.