How the FBI and Investigation Teams Recover Deleted Files and Permanently Delete Them

When files are deleted from a computer, they are not typically removed from the storage medium immediately. Instead, the operating system marks the space occupied by the deleted files as available for new data, but the actual data remains on the drive until it is overwritten. This means that deleted files can often be recovered by forensic experts. Let's delve into how the FBI and other investigation teams perform file recovery, and also explore methods to permanently delete files.

File Recovery Techniques

File Recovery Software

Investigators use specialized software to scan the storage medium to identify and recover deleted files. These tools can often restore files that haven't been overwritten. For example, EaseUS Data Recovery Wizard and Stellar Data Recovery are popular options. These programs are designed to scan hard drives for files that can be recovered, even if the file system no longer recognizes them.

Forensic Imaging

The first step in many investigations is to create a bit-by-bit copy image of the hard drive. This process, known as forensic imaging, preserves the state of the drive, allowing forensic analysts to work on the copy without altering the original evidence. Tools such as FTK imager and EnCase are commonly used for this purpose.

Data Carving

Data carving involves searching for file signatures or patterns to recover files based on their structure, even if the file system no longer recognizes them. This method is used when the file system itself is fragmented or corrupted. Software such as Scalpel and Scorch can be used for data carving.

Magnetic Force Microscopy

Advanced techniques like magnetic force microscopy can be used to analyze the magnetic states of the disk surface, recovering data that might not be accessible through traditional means. This is a highly specialized method that is typically used in the most challenging of cases.

Analysis of File System Metadata

Forensic investigators can also look at the file system's metadata, which may still contain information about deleted files including names, sizes, and timestamps. This can provide valuable clues about the contents of deleted files.

Permanently Deleting Files

Overwriting

Writing new data over the space where the deleted file was stored can make recovery nearly impossible. This is often done using software that overwrites the data multiple times. Tools such as CCleaner and EaseUS Data Recovery Wizard offer options to overwrite files several times, effectively rendering them unrecoverable.

Secure Erase Commands

Many modern hard drives and SSDs have built-in secure erase commands that can be used to wipe the drive clean. These commands ensure that data cannot be recovered. For example, the Secure Erase feature in drives from manufacturers like Western Digital, Seagate, and Samsung can be accessed via software like SDC SafeErase.

Physical Destruction

Physical destruction of the storage medium, such as shredding or incinerating, guarantees that the data cannot be recovered. This is often the most permanent form of data deletion but is used for critical or highly sensitive data. Companies like Shred-It offer commercial-grade shredding services.

Conclusion

In summary, while deleted files can often be recovered by forensic teams, there are methods to make the recovery extremely difficult. By using advanced data recovery methods, overwriting, secure erase commands, or physical destruction, individuals and organizations can protect their data from unauthorized access.