CHFI (312-49) Digital Forensics Simulation
Investigation Scenario
You are a digital forensics investigator examining a Windows 10 workstation in Boston following reports of unauthorized data exfiltration and potential evidence destruction. The primary user denies installing or running any unauthorized software.
During the dead-box examination of the E01 image, you navigate to the C:\Windows\Prefetch directory. Your goal is to establish evidence of program execution, bypassing the user's claim that they "only stored" the suspicious executable on the desktop but never launched it.
Evidence Collected
- Device: Dell OptiPlex Desktop (Windows 10 Pro)
- State: Dead-box analysis (E01 Image Mounted)
- Artifact Location:
C:\Windows\Prefetch - Discovered Artifact:
ERASER.EXE-3F7A9B1C.pf - File Metadata: Created 2026-04-08 14:22:15 UTC
Question
During a forensic examination of a Windows workstation in Boston, an analyst discovers a file with a .PF extension in the C:\Windows\Prefetch folder. What is the primary purpose of these files in a Windows environment?
Expert Analysis
1. What evidence shows
The discovery of a .PF file specifically named ERASER.EXE-3F7A9B1C.pf in the C:\Windows\Prefetch folder directly indicates the operating system's Cache Manager tracked the execution of the "Eraser.exe" program.
2. Identify forensic stage
Examination & Analysis. The investigator is analyzing extracted file system artifacts to build a timeline of application execution on the target device.
3. Why correct answer is correct
A. To improve the startup time of applications is correct. Windows Prefetch monitors the files accessed during the initial 10 seconds of an application's startup. It stores this trace in a .pf file. On subsequent runs, Windows uses this file to preload the required code pages and DLLs into memory, significantly decreasing the application load time. In digital forensics, this mechanism provides undeniable proof that an executable was run on the system.
4. Why others are wrong
B. Web browsing activity is stored in browser-specific databases (e.g., SQLite databases like WebData or History, or older index.dat/WebCacheV01.dat files), not Prefetch.
C. System errors and warnings are recorded in Windows Event Logs (.evtx files located in C:\Windows\System32\winevt\Logs).
D. User passwords are securely hashed and stored in the SAM registry hive or NTDS.dit database in domain environments, never in plaintext or Cache Manager files.
5. Real-world forensic action
A forensic analyst would not just note the existence of the .pf file; they would parse it using tools like Eric Zimmerman's PECmd. Parsing a Windows 10 Prefetch file reveals the application's original executable path, the run count (how many times it was executed), up to the last 8 execution timestamps, and a list of all files/volumes the application interacted with during startup.
MINI LESSON: Prefetch Artifact Analysis
- Artifact Interpretation: The presence of a Prefetch file is absolute proof of execution. Even if a suspect deletes the executable (
.exe), the corresponding.pffile usually remains. - File Naming Convention: The 8-character hex string after the executable name (e.g.,
3F7A9B1C) is a hash of the application's path. This helps differentiate instances of an executable run from different locations (e.g., Desktop vs. Downloads folder). - Forensic Workflow: Extract
.pffile -> Parse with PECmd -> Establish execution timeline -> Correlate with UserAssist registry keys, Amcache, and Windows Event Logs (e.g., Event ID 4688: Process Creation) to build a solid narrative of user activity.