Daily Blog #67 - Understanding the artifacts DeviceClasses

Understanding the artifacts DeviceClasses

Hello Reader,
         Tomorrow is the Forensic Lunch, are you going to join us? Click here to RSVP and be notified when the YouTube link is live! Want to be on the video chat? Email me dcowen@g-cpartners.com and I'll get you in the video chat room.

Today we are going to talk about the DeviceClasses registry key. Introduced in Windows Vista the DeviceClasses subkeys are created when a plug and play device driver is successfully loaded. This is great for us because unlike USBStor/SBP2Stor and IDE it is not confined to any one type of connection and makes it harder to miss connected devices. If you want to read about PnP subsystem and how it updates the registry go here: http://msdn.microsoft.com/en-us/library/windows/hardware/ff558808%28v=vs.85%29.aspx

I most regularly use DeviceClasses on Windows 7 system to determine last plug in times for external storage media. Understanding what it does, why it creates these keys, why there are so many keys and what you should expect to find in them will help you when everything else fails.

The DeviceClasses key found in the System registry under
 contain a number of subkeys, each subkey relates to the type of device that is being recognized. For instance the physical disk of an external drive would be in the GUID key: {53F56307-B6BF-11D0-94F2-00A0C91EFB8B}
reference: http://msdn.microsoft.com/en-us/library/windows/hardware/ff545824%28v=vs.85%29.aspx

While the volume that is mounted would be stored under GUID: {53F5630D-B6BF-11D0-94F2-00A0C91EFB8B}
reference: http://msdn.microsoft.com/en-us/library/windows/hardware/ff545990%28v=vs.85%29.aspx

The full list of storage device types and GUIDs can be found here:

The full list of all GUIDs by category of device can be found here:

Whats important to understand here is that all PnP devices are recorded under these subkeys. If you have a case where you think a non standard device may have been utilized (a voice recorder, a media player without direct physical disk access, web cam, etc...) and a driver installed at one point you should look up the GUID that corresponds to the type of device to review the subkeys and determine what was plugged in.

For example, if you have a USB Storage Device plugged it will add keys to the two GUIDS listed earlier and contain information relevant to the disk/volume. The following examples call from the GUID key:

As an example here is what a Tableau connected via Firewire looks like:
Here is what an eSATA attached SSD looks like:
Here is what a F-Response iSCSI disk looks like:
This is what an external non generic USB Disk looks like:
This is what an external generic USB Disk looks like:
This is what a USB attached android phone looks like:
When looking at the Volume GUIDs you'll see the full key:

A MagicISO mounted image looks like:
The volume of the generic USB storage device we referenced above looks like:
If you haven't taken a look at your own DeviceClasses key go take a look, there may be more facts you can determine from your own usage of your forensic workstation than you thought.

Many times in our analysis we focus on whats common, USB storage is the most common type of external storage for instance. There is no guarantee though that your custodian will oblige your convenience, so if you are dealing with something nonstandard this a great place to determine the last plug in time of your device.

I'll go into key analysis and linkage in the Usage post, so be sure to watch the Forensic Lunch live tomorrow and ask questions!

Also Read: 
Daily Blog #66: Understanding the artifacts setupapi.log/setupapi.dev.log

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