Analyzing Windows Shellbag Artifacts

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

Detection Gaps & Validation

• Shellbags prove Explorer-shell navigation only. Folders reached via cmd, PowerShell, or programmatic APIs leave no Shellbag entry. Absence of a Shellbag is not absence of access — corroborate before clearing a path.
• Most-missed source: UsrClass.dat. On Windows 10/11 the bulk of folder activity lives in UsrClass.dat (Local Settings\...\Shell\BagMRU), not NTUSER.DAT. Parsing only NTUSER drops the majority of evidence; run SBECmd against both hives.
• Timestamp/timezone pitfall: the embedded shell-item dates are local-time DOS dates with 2-second granularity, while CreatedOn/ModifiedOn/AccessedOn reflect view-setting changes, not necessarily a visit. Do not treat them as UTC and do not equate them with first/last access without correlation.
• Batch updates: Explorer can rewrite many Shellbag entries at shutdown, collapsing distinct visits into one timestamp.
• Anti-forensics: deletion of BagMRU subtrees or whole-hive replacement. Recover from VSS and replay .LOG transaction files for dirty hives.
• Validate / cross-corroborate: tie removable/network paths to USBSTOR + MountPoints2 (volume serials), LNK/Jump List targets, RecentDocs, and $MFT/USN entries for the same folder. A folder that "no longer exists" should still reconcile with at least one second artifact before it anchors a finding.

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

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/