Computer Forensics examination of the $USNJRNL 

Computer Forensics uses the $USNJRNL (short for "Update Sequence Number Journal") to provide some critical data and is found on NTFS-formatted Microsoft Windows operating system drives. The computer forensics examiner track changes made to the filesystem. It allows the system to revert to a previous state in the event of a crash or other unforeseen issue. 

The $USNJRNL file is a crucial component of the NTFS filesystem, as it allows the system to keep track of changes made to the drive and maintain data integrity. Without the $USNJRNL file, the system would be unable to properly recover from errors or crashes, potentially leading to data loss or corruption.

Computer forensics examiners track changes made to the filesystem through the forensic artifact of the $USNJRNL. From an operating system prospective, it allows the system to undo the changes if necessary, such as in the event of a crash or power failure. When the changes have been successfully written to the filesystem, the system then updates the $USNJRNL file to reflect the new state of the drive.

Within a computer forensic image the $USNJRNL file is typically located at the root of the drive, along with other important system files such as the Master File Table (MFT) and the Master Boot Record (MBR). It is typically hidden from view. If live forensics is used this file should not be modified or deleted manually, as doing so can cause serious issues with the filesystem.

In addition to tracking changes made to the filesystem, the $USNJRNL file is also used in the process of defragmenting the drive. When a drive is defragmented, the system rearranges the data on the drive to improve performance and optimize access to the files. During this process, the $USNJRNL file is used to ensure that the defragmentation process does not interfere with any ongoing filesystem changes.

A computer forensic examiner will want to pay particular attention to the following entries.

• File create
• File delete
• Rename old name
• Rename new name
• Data overwrite

It's important to note that the $USNJRNL file is not a replacement for regular backups. While the $USNJRNL file can help the system recover from errors and crashes, it cannot protect against more serious issues such as hardware failure or malware infection. As such, it's still important to regularly back up your data to prevent data loss in the event of a catastrophic failure.

In summary, the $USNJRNL file is an important component of the NTFS filesystem, allowing the system to track changes made to the drive and maintain data integrity. It is crucial for the proper functioning of the system, and should not be modified or deleted manually. While it can help with recovery from errors and crashes, it is not a replacement for regular backups.