Windows Prefetch Files: A Forensic Goldmine for Tracking Program Execution

Windows Prefetch is one of the most valuable forensic artifacts for tracking program execution history. By analyzing Prefetch files, investigators can determine which applications were run, when they were executed, how often they were used, and even which files and directories they accessed.

We’ll explore:

✅ What Prefetch is and how it works

✅ Where to find Prefetch files

✅ How to extract and interpret Prefetch data

✅ Best practices for forensic investigations

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What Is Prefetch and How Does It Work?

Windows Prefetching is a performance optimization feature that preloads frequently used applications into memory to speed up their execution.

When a program is launched for the first time, Windows creates a .pf (Prefetch) file for it.

Each .pf file contains:

✅ The name and path of the executed application

✅ How many times it has been executed

✅ The last execution time

✅ Up to 8 previous execution timestamps (Windows 8 and later)

✅ Referenced files and directories the application accessed

💡 Key Insight: If a Prefetch file exists for an application, it proves that the program was executed at least once on the system.

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Where Are Prefetch Files Stored?

On Windows workstations (not servers), Prefetch files are stored in:

C:\Windows\Prefetch\

📌 File Naming Format:

7ZFM.EXE-56DE4F9A.pf

• The ApplicationName is the name of the executable

• The HASH is a hexadecimal representation of the executable's full path.

💡 Pro Tip: If you find multiple Prefetch files with the same executable name but different hashes, it means the program was executed from multiple locations—potentially indicating malware or unauthorized software.

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How Many Prefetch Files Are Stored?

• Windows 7 and earlier → Stores up to 128 Prefetch files

• Windows 8, 10, and 11 → Stores up to 1,024 Prefetch files

📌 Important Note: Older Prefetch files are deleted as new ones are created, meaning execution history may be lost over time.

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Understanding Prefetch Execution Timestamps

💡 How to determine the first and last execution time:

Timestamp Type	Meaning	Accuracy Considerations
File Creation Date	First recorded execution of the application	Only accurate if the .pf file was never deleted due to aging out
File Last Modified Date	Last recorded execution of the application	Subtract ~10 seconds for accuracy
Embedded Timestamps (Windows 8+)	Last 8 execution times	Most reliable for tracking multiple executions

📌 Important Note:If an application was executed before its Prefetch file aged out, a new .pf file is created, making it look like the application was first executed at a later date than it actually was.

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Why Prefetch Files Are Crucial in Digital Forensics

✅ 1. Tracking Program Execution

• Prefetch proves a specific application was run on the system.

• Even if an application was deleted, its Prefetch file may still exist as evidence.

✅ 2. Identifying Suspicious Activity

• If you find a Prefetch file for malware or hacking tools (mimikatz.exe, nc.exe), it indicates they were executed.

• Finding multiple Prefetch files for the same executable in different locations suggests a renamed or relocated executable, which is common for malware evasion techniques.

✅ 3. Detecting Unauthorized Software & Insider Threats

• If a user claims they never used a VPN, but a Prefetch file for NordVPN.exe exists, this contradicts their claim.

✅ 4. Establishing a Timeline of Events

• Prefetch timestamps can help reconstruct a timeline of when certain applications were executed relative to an incident.

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Limitations of Prefetch Analysis

⚠️ 1. Prefetch Is Disabled on Some Systems

• Windows Server OS does not use Prefetch.

• Some Windows 7+ systems with SSDs may have Prefetch disabled.

📌 Check Registry Settings to See If Prefetch Is Enabled:

SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters

Audit the EnablePrefetcher value:

• 0 → Disabled

• 1 → Application launch prefetching enabled

• 2 → Boot prefetching enabled

• 3 → Both application launch & boot prefetching enabled (default)

⚠️ 2. Prefetch Does Not Prove Successful Execution

• A .pf file is created even if the program failed to execute properly.

• Cross-check with other artifacts (UserAssist, BAM/DAM, AmCache) for confirmation.

⚠️ 3. Prefetch Files Are Limited in Number

• Older Prefetch files are deleted when the limit is reached.

• If an app was used long ago, its Prefetch file may no longer exist.

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Best Practices for Prefetch Analysis

🔍 1. Prioritize Prefetch Collection

• Live response tools create new Prefetch files—potentially overwriting older forensic evidence.

• Collect Prefetch data before running analysis tools.

🔍 2. Cross-Reference Other Execution Artifacts

• Compare Prefetch data with:

  • UserAssist 

  • AmCache 

  • BAM/DAM

  
  

🔍 3. Look for Anomalous Prefetch Files

• Multiple Prefetch files for the same application but with different hashes may indicate suspicious execution paths.

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Final Thoughts: Prefetch Is an Essential Artifact for Execution Tracking

Windows Prefetch files are one of the most reliable ways to track program execution. They provide timestamps, execution counts, and file access details that are crucial in forensic investigations.

💡 Key Takeaways:

✅ Prefetch proves an application was executed—even if it was later deleted.

✅ Windows 8+ Prefetch files store up to 8 execution timestamps, making them invaluable for tracking repeat usage.

✅ Prefetch files can reveal unauthorized or malicious software execution.

✅ Cross-check Prefetch data with other execution artifacts (UserAssist, BAM/DAM, AmCache) for accuracy.

🚀 If you're investigating program execution on a Windows system, Prefetch analysis should be at the top of your forensic checklist! 🔍

-------------------------------------------------Dean-----------------------------------------------