agentflocks Analyzing Windows Shellbag Artifacts
Overview
Shellbags are Windows registry artifacts that track how users interact with folders through Windows Explorer, storing view settings such as icon size, window position, sort order, and view mode. From a forensic perspective, Shellbags provide definitive evidence of folder access -- even folders that no longer exist on the system. When a user browses to a folder via Windows Explorer, the Open/Save dialog, or the Control Panel, a Shellbag entry is created or updated in the user's registry hive. These entries persist after folder deletion, drive disconnection, and even across user profile resets, making them invaluable for proving that a user navigated to specific directories on local drives, USB devices, network shares, or zip archives.
When to Use
- When investigating security incidents that require analyzing windows shellbag artifacts
- When building detection rules or threat hunting queries for this domain
- When SOC analysts need structured procedures for this analysis type
- When validating security monitoring coverage for related attack techniques
Prerequisites
- Familiarity with digital forensics concepts and tools
- Access to a test or lab environment for safe execution
- Python 3.8+ with required dependencies installed
- Appropriate authorization for any testing activities
Registry Locations
Windows 7/8/10/11
| Hive | Key Path | Stores |
|---|---|---|
| NTUSER.DAT | Software\Microsoft\Windows\Shell\BagMRU | Folder hierarchy tree |
| NTUSER.DAT | Software\Microsoft\Windows\Shell\Bags | View settings per folder |
| UsrClass.dat | Local Settings\Software\Microsoft\Windows\Shell\BagMRU | Desktop/Explorer shell |
| UsrClass.dat | Local Settings\Software\Microsoft\Windows\Shell\Bags | Additional view settings |
BagMRU Structure
The BagMRU key contains a hierarchical tree of numbered subkeys representing the directory structure. Each subkey value contains a Shell Item (SHITEMID) binary blob encoding the folder identity:
- Root (BagMRU): Desktop namespace root
- BagMRU\0: Typically "My Computer"
- BagMRU\0\0: First drive (e.g., C:)
- BagMRU\0\0\0: First subfolder on C:
Each Shell Item contains:
- Item type (folder, drive, network, zip, control panel)
- Short name (8.3 format)
- Long name (Unicode)
- Creation/modification timestamps
- MFT entry/sequence for NTFS folders
Analysis with EZ Tools
SBECmd (Command Line)
# Parse shellbags from a directory of registry hives
SBECmd.exe -d "C:\Evidence\Registry" --csv C:\Output --csvf shellbags.csv
# Parse from a live system (requires admin)
SBECmd.exe --live --csv C:\Output --csvf live_shellbags.csv
# Key output columns:
# AbsolutePath - Full reconstructed path
# CreatedOn - When the folder was first browsed
# ModifiedOn - When view settings were last changed
# AccessedOn - Last access timestamp
# ShellType - Type of shell item (Directory, Drive, Network, etc.)
# Value - Raw shell item data
ShellBags Explorer (GUI)
# Launch GUI tool for interactive analysis
ShellBagsExplorer.exe
# Load registry hives: File > Load Hive
# Navigate the tree structure to see folder hierarchy
# Right-click entries for detailed shell item properties
Forensic Investigation Scenarios
Proving USB Device Browsing
Shellbag Path: My Computer\E:\Confidential\Project_Files
ShellType: Directory (on removable volume)
CreatedOn: 2025-03-15 09:30:00 UTC
This proves the user navigated to E:\Confidential\Project_Files
via Windows Explorer, even if the USB drive is no longer connected.
The volume letter E: and directory timestamps can be correlated
with USBSTOR and MountPoints2 registry entries.
Detecting Network Share Access
Shellbag Path: \\FileServer01\Finance\Q4_Reports
ShellType: Network Location
AccessedOn: 2025-02-20 14:15:00 UTC
This proves the user browsed to a network share, even if
the share has been decommissioned or access revoked.
Identifying Deleted Folder Knowledge
Shellbag Path: C:\Users\suspect\Documents\Exfiltration_Staging
ShellType: Directory
CreatedOn: 2025-01-10 08:00:00 UTC
Even though C:\Users\suspect\Documents\Exfiltration_Staging
no longer exists, the Shellbag entry proves the user
created and navigated to this folder.
Limitations
- Shellbags only record folder-level interactions, not individual file access
- Only created through Windows Explorer shell and Open/Save dialogs
- Command-line access (cmd, PowerShell) does not generate Shellbag entries
- Programmatic file access via APIs does not generate Shellbag entries
- Timestamps may reflect view setting changes, not necessarily folder access
- Windows may batch-update Shellbag entries during Explorer shutdown
References
- Shellbags Forensic Analysis 2025: https://www.cybertriage.com/blog/shellbags-forensic-analysis-2025/
- SANS Shellbag Forensics: https://www.sans.org/blog/computer-forensic-artifacts-windows-7-shellbags
- Magnet Forensics Shellbag Analysis: https://www.magnetforensics.com/blog/forensic-analysis-of-windows-shellbags/
- ShellBags Explorer: https://ericzimmerman.github.io/
Example Output
$ SBECmd.exe -d "C:\Evidence\Users\jsmith" --csv /analysis/shellbag_output
SBECmd v2.1.0 - ShellBags Explorer (Command Line)
====================================================
Processing hives for user: jsmith
NTUSER.DAT: C:\Evidence\Users\jsmith\NTUSER.DAT
UsrClass.dat: C:\Evidence\Users\jsmith\AppData\Local\Microsoft\Windows\UsrClass.dat
[+] NTUSER.DAT shellbag entries: 456
[+] UsrClass.dat shellbag entries: 1,234
[+] Total shellbag entries: 1,690
--- Folder Access Timeline (Incident Window) ---
Last Accessed (UTC) | Folder Path | Type | Access Count
------------------------|---------------------------------------------------------|-------------|-------------
2024-01-15 14:34:05 | C:\Users\jsmith\Downloads | File System | 45
2024-01-15 14:36:25 | C:\ProgramData\Updates | File System | 3
2024-01-15 15:05:00 | \\FILESERV01\Finance | Network | 2
2024-01-15 15:12:30 | \\FILESERV01\Finance\Q4_Reports | Network | 1
2024-01-15 15:30:00 | E:\ | Removable | 4
2024-01-15 15:30:45 | E:\Backup | Removable | 3
2024-01-15 15:31:20 | E:\Backup\Corporate_Data | Removable | 2
2024-01-15 16:12:45 | \\FILESERV01\HR\Employees | Network | 1
2024-01-15 16:15:00 | \\FILESERV01\HR\Employees\Records_2024 | Network | 1
2024-01-16 02:35:00 | C:\Windows\Temp | File System | 5
2024-01-17 02:44:00 | C:\ProgramData\svc | File System | 2
2024-01-18 01:10:00 | C:\Users\jsmith\AppData\Local\Temp | File System | 8
--- Network Share Access ---
\\FILESERV01\Finance First: 2023-09-10 Last: 2024-01-15
\\FILESERV01\Finance\Q4_Reports First: 2024-01-15 Last: 2024-01-15 (NEW)
\\FILESERV01\HR\Employees First: 2024-01-15 Last: 2024-01-15 (NEW)
\\DC01\SYSVOL First: 2023-03-15 Last: 2024-01-16 (anomalous access time)
--- Removable Device Access ---
E:\ (USB Drive)
Volume Name: BACKUP_DRIVE
First Accessed: 2024-01-15 15:30:00 UTC
Last Accessed: 2024-01-15 15:45:22 UTC
Folders Browsed: 3 (E:\, E:\Backup, E:\Backup\Corporate_Data)
--- Deleted/No Longer Existing Paths ---
C:\ProgramData\Updates\ (folder deleted, shellbag persists)
C:\ProgramData\svc\ (folder deleted, shellbag persists)
C:\Windows\Temp\tools\ (folder deleted, shellbag persists)
Summary:
Total unique folders accessed: 1,690
Network shares accessed: 4 (2 newly accessed during incident)
Removable media: 1 USB device (data staging suspected)
Deleted folder evidence: 3 paths (anti-forensics indicator)
CSV exported to: /analysis/shellbag_output/