Monday, August 13, 2012

Windows Backup and Restore

A recent investigation led me to a Windows Backup file.  Windows 7 as well as Windows Vista includes a utility allowing the user to backup and restore folders, files and system information. This is not the same as Volume Shadow Copies (VSCs), another method wherein Windows backs up files.  For information on how to examine VSCs  check out Harlan Carvey's book, or other blog posts here and here.  Depending on the version on Windows, the backup can be stored on an external device, such as USB drive or over the network (Windows 7 Pro/Ultimate).   My research was done with Windows 7 Home Premium and Ultimate.

Windows creates a backup with the following naming convention:
ComputerName\Backup File YYYY-MM-DD ######\Backup files

Interestingly enough, if an end user looks at this backup through Windows, they will only see the top level folder:


Windows Backup creates multiple zip files containing the files/folders that where backed up. True, if you mount the zip files in your favorite all in one forensic tool you will have access to all these files in their glory. You can run keyword searches until you are giddy, and forensicate to your heart’s content, BUT the dates in the zip file are the dates the backup was created, not the date the file was originally created or modified.  That being said, Windows Backup tracks these original dates which may come in handy.

Windows Backup tracks the names of the folders, files and original dates in a file named GlobalCatalog.wbcat under ComputerName\Backup File YYYY-MM-DD ######\Catalogs. If you do not have access to the back up media, a local GlobalCatalog.wbcat file is created. I discuss this in more detail below.
Ideally, this file could be parsed for all of this information, with the results displayed in a nice format, CSV or otherwise.  I have been looking at this file in hex trying to figure out a way to accomplish this. So far, I have located the file names, folders and dates, but have not figured out how the records are tied together within the file.  Boooo…. If you know of any existing program or script that can parse the data, or know the file format, please let me know. If you are interested in seeing a sample of what I have located so far, contact me (arizona4n6 at gmail dot com) and I can send it to you.

As such, viewing the backup file natively through Windows Backup is the only method I have discovered  to see the original dates for the files and folders. Step by Step directions follow: 
  •  Export the backup files from your image to an external device. If you prefer to mount the image, create a VHD using Vhdtool  on a DD image and attached the VHD through the Disk Manager. Make sure its a copy of your image as Vhdtool will make changes to it.  This should sound familiar if you have read Harlan's Post on using the Vhdtool to examine VSCs. I tried to mount the image using FTK Imager and the backup file was not seen by Window's Backup.
  •  Launch Windows Backup and Restore (Control Panel>System and Security>Backup Your Computer).
  •   Got to Restore>Select another backup to restore files from. It should auto locate the Windows Backup.

  • Next, Search for *.*, and all the files will be listed or you can browse to a particular file if you please. By default, only the Date Modified is listed.  If you right click the title bar, you can select the Date Created as well. If you use the Browse function instead of Search, you will also have the option to see the backup date.

Now, instead of seeing all the same dates and times for the files contained within the zip files, you are presented with the original Date Created and Date Modified for files. As I mentioned before, it would be soooooo nice to have this information parsed directly from the GlobalCatalog.wbcat file.

Windows Backup Registry Entries
When a Windows Backup is created an entry is made or updated in the Software Hive under the key \Microsoft\Windows\ CurrentVersion\WindowsBackup\.

This key holds various sub keys with information regarding the backup including USB device information. This USB information may come in handy if you are also conducting link analysis/USB analysis and can be cross referenced with other registry keys.

Some of the information available with sample data :

Target Device

For a USB Device:

  PresentableName = E:\
  UniqueName = \\?\Volume{a2e6b4d4-e492-11e1-a39d-000c29448ee3}\
  DeviceVendor  = SanDisk
  DeviceProduct  = Cruzer
  DeviceVersion  = 1.26
  DeviceSerial = 200605999207D70370EF         

 For a Network Share:

  PresentableName = \\COMPUTERNAME\Users\Public\Documents\backup\
  UniqueName = \\?\UNC\COMPUTERNAME\Users\Public\Documents\backup\

  LastResultTime = Sun Aug 12 17:45:39 2012 (UTC)
  LastSuccess = Sun Aug 12 17:45:39 2012 (UTC)
  LastResultTarget = \\?\Volume{a2e6b4d4-e492-11e1-a39d-000c29448ee3}\
  LastResultTargetPresentableName  = E:\
  LastResultTargetLabel = MYTHUMBDRIVE

According to my testing, the LastResultTime and LastSuccess will be the same if the backup completed. If the backup did not complete or was cancelled, these times will be different, and the LastResultTime will contain the time of the attempted backup.

I have created an Reg Ripper plugin and passed it along.  It should be included in the next disto.
Other Artificats
A Volume Shadow Copy is created before the backup.

Event log entries in \Windows\System32\winevt\LogsMicrosoft-Windows-WindowsBackup%4ActionCenter.evt

Local GlobalCatalog files created:

    \System Volume Information\Windows Backup\Catalogs\GlobalCatalogCopy.wbcat

    \System Volume Information\Windows Backup\Catalogs\GlobalCatalog.wbcat

This local GlobalCatalog.wbcat file seems to contain not only entries for the last backup, but for previous backups done, as well as previous media used. This could be helpful if you need to locate/subpena various devices that contain backups. Below are some results from running Strings across this file:

COMPUTERNAME\Backup Set 2012-08-11 213315\Backup Files 2012-08-11 213315\Backup files
COMPUTERNAME\Backup Set 2012-08-11 213315\Backup Files 2012-08-11 213315\Backup files
Backup Set 2012-08-12 194644
COMPUTERNAME\Backup Set 2012-08-12 194644\Backup Files 2012-08-12 194644\Backup files
DataTraveler SE9
COMPUTERNAME\Backup Set 2012-08-12 194644\Backup Files 2012-08-12 194644\Backup files
COMPUTERNAME\Backup Set 2012-08-12 194644\Backup Files 2012-08-12 203800\Backup files
COMPUTERNAME\Backup Set 2012-08-12 194644\Backup Files 2012-08-12 203800\Backup files

As I mentioned before, I am trying to figure out the GlobalCatalog file format, so if you know the file format, or any tools that can parse it, please let me know :-) 

1 comment:

  1. Windows Backup and Restore option are really good for me. Because at this time create more problems about it. So you can giving to me greatest information about it. Thanks for sharing to good information.