WinObj is a free Sysinternals tool that lets you examine the Windows Object Manager’s namespace. It provides a visual tree of the internal, hidden objects that the Windows operating system uses to manage resources like processes, files, and hardware drivers.
Here is a practical tutorial on how to use WinObj to analyze system handles and object directories. Understanding the Basics
The Windows Object Manager organizes system resources in a hierarchical directory structure, much like files and folders on a hard drive.
Object Directories: Visual folders in WinObj (e.g., \Device, \RPC Control) that group related system objects.
Objects: The actual resources inside directories, such as symbolic links, events, mutations (mutexes), and device drivers.
Handles: Direct pointers or references that running programs use to talk to these objects. Step-by-Step Guide to Exploring WinObj 1. Run with Administrator Privileges
To see the complete object namespace, you must run WinObj as an administrator. Download WinObj from Microsoft Sysinternals. Right-click WinObj.exe and select Run as administrator.
If you do not run it as admin, many directories will appear empty due to security permissions. 2. Navigate Key Object Directories
When you open WinObj, you will see a tree view on the left pane. Here are the most critical directories to analyze:
</code> (Root): The top of the namespace containing all other directories.
\Device: Contains functional device objects created by hardware and software drivers (e.g., hard drives, network cards, keyboard drivers).
\DosDevices (or \??): Holds symbolic links that map traditional DOS drive letters (like C:) to their actual NT device paths (like \Device\HarddiskVolume3).
\RPC Control: The communication hub for Remote Procedure Calls (RPC). Malware and system services often use these ports to communicate locally.
\BaseNamedObjects: The default location where standard user applications create shared objects like Mutexes, Events, and Semaphores to sync data between processes. 3. Analyze Object Properties
Click on any directory in the left pane to view its contents in the right pane.
Identify the Type: The “Type” column tells you what the object does (e.g., Driver, SymbolicLink, Section, Event).
Check Symbolic Links: If an object is a SymbolicLink, the “Link Target” column shows exactly where that link points.
View Permissions: Right-click any object and select Properties, then click the Security tab. This shows which user accounts or system processes have permission to access or modify that specific object. Analyzing Handles via the Object Manager
While WinObj shows you the existential map of all active objects, you often need to see which running programs hold handles to them.
Because WinObj provides a static snapshot of the namespace layout, you should pair it with Process Explorer (another Sysinternals tool) for active handle analysis:
Find an Object in WinObj: Locate a specific device or mutant name (e.g., a Mutex used by an application under \BaseNamedObjects).
Search in Process Explorer: Open Process Explorer, press Ctrl + F, and type the name of the object you found in WinObj.
Identify the Owning Process: Process Explorer will list every running program that currently holds an active handle to that object.
Close Handles Safely: If a file or resource is “locked,” finding its handle allows you to close the handle or terminate the owning process to free up the resource. Practical Use Cases for IT Pros and Developers
Debugging Deadlocks: Developers use WinObj to verify if their software is correctly creating Named Mutexes or Events in \BaseNamedObjects to prevent multiple app instances from crashing each other.
Malware Analysis: Reverse engineers look at \RPC Control and \BaseNamedObjects for unusual, randomly named Mutexes or ALPC ports, which malware frequently uses for inter-process communication or persistence.
Troubleshooting Hardware Drivers: If a storage drive or USB device isn’t responding, checking \Device and \DosDevices confirms if the OS actually created the virtual device object and mapped the drive letter properly.
To help tailor this tutorial, could you tell me more about your specific goal? If you let me know if you are troubleshooting a locked file, analyzing malware, or writing your own Windows driver, I can provide the exact steps for that scenario.