INFO[rmation fo]RENSICS

A simple plan to ruin your boss: plant child porn on his PC.

This occurred in the UK in 2006 (it is just now working its way through the courts), and seems extreme.  The reality is that planted evidence can occur in many different forms:  Planted documents, images, and even emails.

While the deception in the UK case was broken through cell phone activity (the perpetrator made an “anonymous” phone call, and had been heard bragging about his exploits at a BBQ), a good forensic examiner goes beyond simple modified, accessed and created times to review other system information that backs up the method of arrival of the information on the system itself:

• The insertion of USB devices: USB devices can leave quite a trail on a system, including the device manufacturer, type, even sometimes serial numbers.  Further activity supporting the insertion of the device can sometimes be correlated between file history analysis and searches for activity surrounding the specific device ID.
• Metadata contained within the purported documents: Images, videos, audio files, PDF documents and other file types often have information regarding the date of creation (not necessarily introduction to the system), authorship, serial or license numbers of the product used, sometimes even information about the system that created them.
• System files: Sometimes the introduction or generation of a file triggers other supporting files on the system.  Examination of these files can tell an investigator whether the file information matches up with what the system knows about the file.
• Surrounding activity: Other activity on the system related to usage can be an indicator as well.  For example: If a file was supposedly downloaded from the internet, one would expect to see certain other activity surrounding the download if it was generated by the user.

A lot of these same techniques can be used to attack or defend other claims of the so-called “trojan defense” (aka “A Virus must have done it”).

Researching deliberate obfuscation CAN be a challenge, but in situations similar to the UK case a client is not at all dead in the water if an information forensics analyst is competent and able to look at the “Evidence Beyond the Hard Drive”™.