2. Volume Shadow Copy (VSC) in use
• VSC Enables the
‘Previous Versions’
functionality in Windows 7
• Similar functionality called
‘File History’ is used in
Windows 8
4. VSC
• Uses
• Previous Versions/File History functionality
• Create System Restore Points
• Backup API for taking ‘Snapshots’ of files/folders/disk
• Used by Windows Backup, Hyper-V, Virtual Server, Active Directory,
SQL Server, Exchange Server & SharePoint
• Used by backup software & AV for reading locked (in-use) files
• Implementation
• Only for NTFS volumes
• Volume ShadowCopy Service (VSS)
• Included in Windows 2003 onwards including Windows 8
• Not enabled by default on Windows 2008 or 2008 R2
5. Location of Backups/Restore Points
• Default
• <Drive Letter>:System Volume Information
• Applications can use API to write to any location
6. Volume Shadow Copy
• C:System Volume Information
Figure: ‘C:System Volume Information’ Folder viewed in Encase 6
7. Forensic Importance
• Shadow copies are the source data for Restore Points
and the Restore Previous Versions features
• Shadow copies provide a “snapshot” of a volume at a
particular time
• Shadow copies can show how files have been
altered/modified
• Shadow copies can retain data that has subsequently
been deleted, wiped, or encrypted
8. However...
Volume shadow copies DO NOT contain a complete image
of everything that was on the volume at the time the
shadow copy was made!
Figure: Settings for VSC located in Registry at:
HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlBackupRestore
9. Basic Technical Details
• Volume shadow copies are bit level differential backups of
a volume
• NOT File level backups
Driver Stack
File
Volume
• Scheme
• 16 KB blocks Disk
• Copy on write
• Volume Shadow copy files are “difference” files
10. Copy-on-write illustration
Raw Disk blocks
0 1 2 3 4 5 6
16 KB Info.txt
Amit.pdf
36 KB 32 KB
Flier.PPT
10 KB
Operations
1. Edit & save Info.txt
6 1 2 3 6
2. Delete Amit.pdf
3. Edit & save Info.txt
Resulting VSC file has copies of only modified
blocks
11. Recreating the volume in time
• VSC by itself does not have all data
• Only modified blocks are saved
• Need volume itself to recreate complete disk
Volume
0 1 2 3 4 5 6
(NOW)
VSC
6 1 2 3 6
data
Volume
0 1 2 3 4 5 6
(before all
operations)
12. VSC File Format
File Description
{3808876b-c176-4e48-b7ae-04046e6cc752} Catalog only
{GUID}{3808876b-c176-4e48-b7ae-04046e6cc752} Catalog and data
HEADER CATALOG DATA STORES
Contains VSS Contains Shadow copy Contains details of shadow copy
identifier and GUIDS, creation times, providers, host machine info,
Catalog offset store offsets, etc.. volume bitmaps and the associated
data
15. List files in shadow copy
• Commands:
vssadmin list shadows
set shadow=?GLOBALROOTDeviceHarddiskvolumeshadowcopyxx
for /R %shadow% %i in (*) do echo %i
Or
for /R %shadow% %i in (*) do echo %i>>"C:shadow.txt"
16. Investigate Shadow Copies from another
disk
• Commercial software
• Use Encase Physical Disk Emulator and manual approach using
command line / PowerShell
• X-ways Forensic (XWF)
• Shadow Scanner from EKL
• Reconnoitre from Sanderson Forensics
• ProDiscover
17. Investigate Shadow Copies from another
disk
• FREEWARE approach 1
• Use FTK Imager to mount your evidence disk as a physical device
• Add the mounted disk as a new Hard Disk to an existing Windows
7 Virtual Machine (VM) in VMware Player (or VirtualBox)
• Boot VM, now vssadmin should be able to see the snapshots
• Use manual approach to list / parse / copy out
• FREEWARE approach 2
• Use Joachim Metz’s libvshadow project
(https://code.google.com/p/libvshadow/)
• Mounts your shadow copies in a linux enviroment
18. FTK Imager + VMware
FTK Imager Mount Settings
VM settings (added new Hard
Disk)
19. Questions
Thanks for listening!
More forensic articles, tips and scripts on my blog –
www.swiftforensics.com
Yogesh Khatri
Director, Training & Services
W.H.S.
yogesh.khatri@whitehats.in
yogesh@swiftforensics.com
