Cloned Drive Data Integrity

TL;DR

Yes, data can be tampered with after a drive is cloned, even if the clone appears identical. This is because cloning creates a copy, not an exact mirror of the original at a specific point in time. Changes made to either the original or the clone are independent. To ensure data integrity for forensic purposes or reliable backups, use imaging software instead of simple cloning tools.

Understanding Cloning vs Imaging

It’s important to understand the difference between drive cloning and disk imaging:

• Cloning: Copies all sectors from one drive to another. It’s a fast process, but it copies everything – including deleted files, empty space, and potentially corrupted data. Changes after cloning are not reflected in either drive.
• Imaging: Creates a single file (an image) that represents the entire drive. This is like taking a snapshot of the drive at a specific moment. It’s slower than cloning but provides a more reliable backup or forensic copy.

Why Data Can Be Tampered With After Cloning

1. Independent Changes: Once cloned, both drives operate independently. If you modify files on the original drive after cloning, those changes won’t appear on the clone and vice-versa.
2. File System Updates: File systems (like NTFS or FAT32) track file locations and metadata. Cloning copies this information as it is at that moment. Subsequent writes to either drive update their respective file system records.
3. Time Stamps: File timestamps are updated when files are modified, created, or accessed. These timestamps will differ between the original and the clone if changes occur after cloning.

How to Prevent Data Tampering

To ensure data integrity, use disk imaging software instead of cloning tools.

Step 1: Choose Imaging Software

Several excellent imaging tools are available:

• dd (Linux/macOS): A powerful command-line tool.
• Clonezilla: Free and open-source, with a graphical interface.
• FTK Imager: Popular for forensic imaging.
• Win32 Disk Imager: Simple to use on Windows.

Step 2: Create the Image

The process varies depending on the software, but generally involves selecting the source drive and a destination file or location.

Example using dd (Linux):

sudo dd if=/dev/sda of=/path/to/image.img bs=4M status=progress

Important: Be very careful when using dd, as specifying the wrong source or destination can lead to data loss.

Step 3: Verify the Image

After creating the image, it’s crucial to verify its integrity. Most imaging tools offer verification options (e.g., calculating checksums like MD5 or SHA256).

Example using md5sum (Linux):

md5sum /path/to/image.img

Compare the generated checksum with a known good value if available.

Step 4: Write-Protect the Original Drive

To prevent accidental modifications to the original drive, use hardware write blockers whenever possible. These devices physically prevent any writes to the source disk during imaging.

Forensic Considerations

1. Chain of Custody: Maintain a detailed record (chain of custody) documenting every step taken with the drives and images, including dates, times, personnel involved, and software used.
2. Hashing: Calculate cryptographic hashes (MD5, SHA1, SHA256) of both the original drive and the image to verify their integrity throughout the investigation.
3. Write Blockers: Always use a hardware write blocker when imaging evidence drives.

Summary

While cloning is useful for quick backups, it doesn’t guarantee data integrity. For situations where preserving the original state of a drive is critical (e.g., forensic investigations or reliable disaster recovery), disk imaging with verification and write protection is essential. Remember that cyber security best practices include verifying all copies of important data.