What device is essential for making a forensically sound copy of a hard disk?

A write blocker is essential for making a forensically sound copy of a hard disk because it allows the data to be copied without modifying or altering the original information on the disk. This device acts as a protective barrier, enabling investigators to access and transfer data while preventing any writing of new data to the storage device. Ensuring that the original evidence remains unaltered is critical in forensic investigations, as any changes can compromise the integrity of the evidence and render it inadmissible in court.

On the other hand, a hard disk formatter is designed to prepare a disk for use by erasing all data and setting up a file system, which would not aid in preserving original data. Data recovery software is typically utilized to retrieve lost or deleted files from damaged disks rather than creating a forensic copy. A disk defragmenter is used to reorganize data on a disk for better performance and does not relate to the process of copying data in a forensically sound manner.