Erased, but Not Gone: Mitigating Anti-Forensic Activities


Lindsay H. Gill, CFE, Director of Forensic Technology
Forensic Strategic Solutions

News stories would lead you to believe that once an email or file is deleted, all hope is lost. Take heart — deleted data will not leave your investigation DOA. The mere absence of the information combined with other artifacts left behind can prove valuable to your investigation.

One of the latest challenges facing forensic analysts is the use of anti-forensic tools. While most frauds leave behind a digital footprint, the more technologically savvy fraudsters are now using anti-forensic tools to encrypt, delete or destroy data. Their goal, of course, is to make it more difficult to uncover the footprints of fraud.

Luckily, there are a few prevalent anti-forensic tools that can help you overcome them:

Hiding data through encryption
The encryption of data encodes it, leaving it unreadable without authorization. While organizations often deploy encryption for security measures, a fraudster may use encryption to obfuscate nefarious activity. Some encryption tools leave a signature on the digital media indicating the presence of an encrypted volume. The challenge created by encrypted data is the need for the encryption key to access the information — without it you are left with few options. But fear not, the mere existence of encryption software may be the smoking gun you need to show concealment.

Deletion of data
Deleted data is possibly the easiest form of anti-forensic activity to address. The delete key on a keyboard would be more accurate if it simply read, “hide.” When data is “deleted” the location where the data resides is merely marked as available — leaving the original data intact until it is overwritten by new data. There are many forensic analysis tools that can identify and recover deleted files or fragments of deleted files not fully overwritten. Information about the deleted files, such as the date of deletion, often proves to be a valuable artifact in an investigation.

Destruction of data
The use of data wiping software is one method a fraudster can use to make it more difficult to restore deleted data. Data wiping will overwrite the free space marked as available when the file was deleted, likely leaving it unrecoverable. The wipe can be performed on an entire disc or a specific area. The good news is that wiping software leaves a footprint that can be useful to your investigation. Review the computer’s program list for wiping tools and document the steps you take in an attempt to recover the “wiped” files. The existence of a wiping program and your efforts to recover the data may serve as evidence of the lengths a suspect went to in an attempt to conceal wrongdoing.

As fraudsters become savvier, investigators will see more sophisticated anti-forensic activity to cover the suspect’s tracks, but remember, even anti-forensic activity leaves valuable evidence.