Reconstructing Windows execution history through disk artifacts

// Overview of Disk Artifacts in Windows

Disk artifacts are remnants of activity left behind by the operating system and installed applications. These artifacts can include prefetch files, registry entries, and event logs, each holding valuable information about executed programs and user actions. Understanding how to analyze these artifacts helps in reconstructing execution history effectively.

// Key Artifacts to Analyze

1. Windows Event Logs: Windows logs contain information about system events, including application starts and stops. They can be accessed via the Event Viewer or directly from the log files.

2. Prefetch Files: Located in C:\Windows\Prefetch, these files help speed up application launches by caching information about the application execution. Each prefetch file is named after the application's executable and provides timestamps of the last execution.

3. Registry Hives: Specifically, the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall key contains details about installed applications, their versions, and last modified timestamps.

4. USN Journal: The Update Sequence Number (USN) journal tracks changes to the NTFS volume. It can be invaluable for determining when files were created, modified, or deleted.

// Step-by-Step Analysis Process

Step 1: Collecting Artifacts

Use tools like Forensic Toolkit (FTK) or EnCase to create a disk image of the target system. Ensure that the image is acquired in a forensically sound manner to maintain integrity.

Step 2: Analyzing Prefetch Files

Prefetch files have the .pf extension and contain execution timestamps and paths of the executable.

Run the following command to list prefetch files:

Get-ChildItem -Path C:\Windows\Prefetch -Filter *.pf | Select-Object Name, LastWriteTime

This command retrieves the name and last write time of each prefetch file. Pay attention to the timestamps, as they reveal when each application was last executed.

Step 3: Inspecting Event Logs

Use wevtutil to export Windows event logs for detailed analysis:

wevtutil export-event-log Security C:\Logs\SecurityLog.evtx
wevtutil export-event-log Application C:\Logs\ApplicationLog.evtx

After exporting, open the logs using a suitable viewer. Look for Event ID 4688, which indicates a new process creation. Here’s what you’ll typically extract:

• Event ID: 4688
• Subject: User account that created the process
• New Process Name: Full path of the executable
• Creation Time: When the process was initiated

Step 4: Examining the Registry

To check application execution from the registry, use reg.exe:

reg query HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall

This command lists installed applications along with their respective uninstall keys, allowing you to trace back the installation and any potential usage of the applications.

Step 5: USN Journal Analysis

If you have access to the USN Journal, you can analyze it for file activity. Use USN Journal Viewer or similar tools to extract information. You can convert USN entries into a readable format using scripts or specialized tools. This data can provide timestamps for file access, which is essential for correlating user activity.

// Common Pitfalls

• Neglecting Volatility: Always remember that volatile data may change or be lost. Capture memory first if the operational context allows.

• Ignoring User Profiles: Check user-specific artifacts located in C:\Users\<username>\AppData\... as they may contain additional execution details relevant to the analysis.

• Overlooking Cleanup: Be aware that some tools or malware may manipulate or delete prefetch and log files to obfuscate execution history. Always corroborate findings with multiple sources.

// Practical Scenario

Consider a case where a suspicious executable was reported. By analyzing prefetch files, you find the associated file was executed multiple times over the last week. Cross-referencing with event logs shows that the executable was run under a specific user account. Further registry checks reveal that the application was installed recently, pointing to a potential security incident.

// Conclusion

The reconstruction of execution history through disk artifacts is a multi-faceted process requiring careful consideration of various data sources. By utilizing Windows event logs, prefetch files, registry keys, and the USN journal, practitioners can build a robust timeline of activities that aid in incident response and forensic investigations. Always ensure to validate findings across multiple artifact types to avoid drawing incorrect conclusions.

--- // FIELDOPS REPORT AUTHORIZED BY: Bruce H. //