Daily Blog #36: Sunday Funday 7/28/13 Winner!

Sunday Funday Winner by David Cowen - Hacking Exposed Computer Forensics Blog

Hello Reader,
                This Sunday Funday I thought was easier than the last and we had several submissions both post on the blog and submitted anonymously but only one was done before the deadline of Midnight PST. o congratulations go out to Jonathan Turner who while not having the most complete answer of all the ones submitted, that goes to Harlan Carvey this week, as he was the only one who submitted his answer before the cutoff!

I got a lot of answers after, do you need me to change the rules to give you more time to play? I thought 24 hours (I try to post at Saturday midnight CST) was enough time, but you need more time to play I can change the rules to let more people participate. I'm hoping as these contests continue we will continue to get great prizes to give away that will tip you over the 'should I try this one' cliff.

Here was the challenge:
The Challenge:     I'm going to step down the difficulty from last week, I may have been asking for a bit much on a Sunday. So this weeks question is going back to basics:


For a Windows 7 system:


Your client has provided you with a forensic image of a laptop computer that was used by an ex-employee at their new employer, it was obtained legally through discovery in a litigation against them. You previously identified that the employee took data when they left where on the system would you look for the following:


1. The same external drive was plugged into both systems.


2. What documents were copied onto the system.


3. What documents were accessed on the system

Here is Jonathan's answer:
1) The manufacturer, model, and serial number of USB keys plugged into a system are stored in the registry at HKLM\SYSTEM\Control\(CurrentControlSet|ControlSet001|ControlSet002)\Enum\USBSTOR. Comparing these keys on the two systems should show any common devices.
2) The created timestamp on the above registry key can be used to filter a timeline of file creation times to determine what files were added to the system around the time it was plugged in. These files could contain metadata about where they were originally created as well as other interesting information that can be manually collected.
3) Documents accessed on the system should show up in jump lists and (potentially) shellbag information stored in the users' ntuser.dat hive.

 Here is Harlan's answer:
Sorry this is late, but I was at a couple of events yesterday starting at around 2pm...I'm not sending it in so much as a submission, but more to just provide my response...

*1. The same external drive was plugged into both systems

This type of analysis starts with the Enum\USBStor keys.  I would locate the subkey that contained the device identifier for the external drive in question, and see if there is a serial number listed.  If not, that's okay...we have other correlating information available.  If there is a serial number pulled from the device firmware, then we're in luck.  

Beneath the device serial number key, I can get information about when the device was first plugged in, from the LastWrite time to the LogConf key, as well as the Data value (FILETIME time stamp) from the \Properties\{83da6326-97a6-4088-9453-a1923f573b29}\00000065\00000000 subkey.  I would correlate this time with the value in the setupapi.dev.log file, as well as with the first time for that device that I found in the Windows Event Log (for device connection events).    I could then get subsequent connection times via the Windows Event Log, as well as the final connection time from the NTUSER.DAT hive for the user, via the MountPoints2 key (for the device, given the volume GUID from the MountedDevices key) LastWrite time value.  

To be thorough, I would also check beneath the \Enum\WpdBusEnumRoot\UMB key for any volume subkeys whose names contained information (device ID, SN) about the device in question.

Getting the disk signature for the specific external drive can be difficult on Win7, using just the System hive file, as there is very little information to correlate the Enum\USBStor information to the information in the contents of the MountedDevices key.  However, further analysis will be of use, so keep reading.  ;-)

The "\Microsoft\Windows NT\CurrentVersion\EMDMgmt" key in the Software hive contains a good deal of information regarding both USB thumb drives and external drives; the subkeys will be identifiers for devices, and for external drives, you'd be interested in those that do NOT start with "_??USBSTOR".  The subkey names will have an identifier, as well as several underscores (""); if the name is split on underscores, the first to the last item, if there is one, will be the volume name, and the last item will be the volume serial number, listed in decimal format.  This final value changes if the device is reformatted, but it wouldn't make any sense to copy files to the device, reformat, and then connect it to the target device, so we can assume that this information won't change between the two systems.

I could then use this information to correlate to LNK files in the Windows\Recent and Office\Recent folder within the user profile, as well as LNK streams within the user's *.automaticDestinations-ms Jump Lists.

At this point, I will have a drive letter that the external drive was mapped to, so I can then return to the MountedDevices key in the system hive, and by accessing available VSCs, locate one in which the drive letter was available for the ext. drive.  This will provide me with the disk signature of the device itself, as well as the volume GUID.

At this point, I have device identifier, the device serial number, the volume serial number, potentially the disk signature, and the time(s) of when the external drive had been connected to the laptop.  I can then use this information to correlate to the other system.

*2. What documents were copied onto the system

I would create a timeline of system activity, correlating file creation dates on the system with times when device was connected to the system, based on the time-based information provided in the response to #1 above. 

*3. What documents were accessed on the system

The shellbags artifacts likely won't server you much use this time, as on Win7, they tend to not contain the same sort (and volume) of information as they do on WinXP.  However, I would start by looking at the shortcut/LNK files in the user's profile (Windows\Recent and Office\Recent), as well as Jump Lists.  This information also helps us identify the application used to access the documents (Office, Adobe, etc).  I would also, for clarity sake, verify this information via Registry MRUs, even though some of them (ie, RecentDocs) will not contain full path information.  However, now that we have information about the applications used (from the Jump Lists, after performing any required AppID lookups), I would be sure to examine any available application-specific MRUs.

Harlan gave a great answer but didn't get in on time, so the winner of a Specialist Track ticket to PFIC is Jonathan Turner. There is still more to be said on this topic though. I use specific operating systems for a reason as artifacts change between them and there are still artifacts and scenarios not clearly being shown even in both of these answers. When I'm done with the web 2.0 series I'll go into depth on it.

In the mean time, do you want to go to PFIC? I still have more tickets to give away next week. If two answers make it in on time that are both great (or I change the rules based on your feedback to extend the time), I can give away more than one! Tomorrow we resume the web 2.0 series and I hope you follow along as it continues to give me the motivation to keep these up daily! Only 316 more blogs before the year is up!

Also Read: Daily Blog #35

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