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

## 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