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When determining which programs were executed on a Windows system and when
During malware investigations to confirm execution of suspicious binaries
For establishing a timeline of application usage during an incident
When correlating program execution with other forensic artifacts
To identify anti-forensic tools or unauthorized software that was run
Detection Gaps & Validation
Prefetch disabled or absent != no execution: Prefetch is off by default on Windows Server, and on SSD systems EnablePrefetcher is often set to 0. An empty or sparse C:\Windows\Prefetch\ does not mean nothing ran - confirm the policy at HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters before concluding "no execution," then pivot to Amcache/ShimCache/SRUM/Event Logs.
Most-missed details inside the .pf: parse the up-to-8 last-run timestamps (not just the most recent), the run count, and the referenced-file list (loaded DLLs, opened data files). The embedded path hash matters: a hash that doesn't match the on-disk path means the binary ran from a different location (USB, deleted folder) than where it now sits.
Anti-forensics that defeats this analysis: attackers delete individual .pf files or clear the folder - a present executable with no Prefetch, or a folder with fewer files than an active system accumulates, is itself suspicious. Recover deleted .pf from $MFT/unallocated and Volume Shadow Copies, and corroborate the gap with USN delete events.
Validate with a second source: Prefetch proves a binary executed at least once - confirm the what/when against Amcache (Amcache.hve), ShimCache (AppCompatCache), SRUM, Security 4688 / Sysmon 1 process-creation events, and the on-disk file's $MFT times before attributing a run to a user or time.
Interpretation pitfalls (false positives): the last-run time is when the prefetch was written (~10s after launch start, with historical caveats), run count can reset, and renamed malware (e.g. svchost.exe from %TEMP%) hides behind a trusted name - check the path hash and referenced files, not the filename. Confirm system timezone and clock skew.
Prerequisites
Access to Windows Prefetch directory (C:\Windows\Prefetch) from forensic image
PECmd (Eric Zimmerman), WinPrefetchView, or python-prefetch parser
Understanding of Prefetch file format (versions 17, 23, 26, 30)
Windows system with Prefetch enabled (default on client OS, disabled on servers)
Knowledge of Prefetch naming conventions (APPNAME-HASH.pf)
Workflow
Step 1: Extract Prefetch Files from Forensic Image
# Mount the forensic image
mount -o ro,loop,offset=$((2048*512)) /cases/case-2024-001/images/evidence.dd /mnt/evidence
# Copy all prefetch filesmkdir -p /cases/case-2024-001/prefetch/
cp /mnt/evidence/Windows/Prefetch/*.pf /cases/case-2024-001/prefetch/
# Count and list prefetch filesls -la /cases/case-2024-001/prefetch/ | wc -l
ls -la /cases/case-2024-001/prefetch/ | head -30
# Hash all prefetch files for integritysha256sum /cases/case-2024-001/prefetch/*.pf > /cases/case-2024-001/prefetch/pf_hashes.txt
# Note: Prefetch filename format is EXECUTABLE_NAME-XXXXXXXX.pf# The hash (XXXXXXXX) is based on the executable path# Same executable from different paths creates different prefetch files
Step 2: Parse Prefetch Files with PECmd
# Using Eric Zimmerman's PECmd (Windows or via Mono/Wine on Linux)# Download from https://ericzimmerman.github.io/# Parse a single prefetch file
PECmd.exe -f "C:\cases\prefetch\POWERSHELL.EXE-A]B2C3D4.pf"# Parse all prefetch files and output to CSV
PECmd.exe -d "C:\cases\prefetch\" --csv "C:\cases\analysis\" --csvf prefetch_results.csv
# Parse with JSON output
PECmd.exe -d "C:\cases\prefetch\" --json "C:\cases\analysis\" --jsonf prefetch_results.json
# Output includes for each file:# - Executable name and path# - Run count# - Last run time (up to 8 timestamps in Windows 10)# - Files and directories referenced during execution# - Volume information (serial number, creation date)# - Prefetch file creation time
Step 3: Parse with Python for Linux-Based Analysis
pip install prefetch
python3 << 'PYEOF'
import os
import json
from datetime import datetime
# Parse prefetch files using python
import struct
def parse_prefetch(filepath):
"""Parse a Windows Prefetch file."""
with open(filepath, 'rb') as f:
data = f.read()
# Check for MAM compressed format (Windows 10)if data[:4] == b'MAM\x04':
import lznt1 # or use DecompressBuffer# Windows 10 prefetch files are compressedprint(f" [Compressed Win10 format - use PECmd for full parsing]")
return None
# Version 17 (XP), 23 (Vista/7), 26 (8.1), 30 (10)
version = struct.unpack('<I', data[0:4])[0]
signature = data[4:8]
if signature != b'SCCA':
print(f" Invalid prefetch signature")
return None
file_size = struct.unpack('<I', data[8:12])[0]
exec_name = data[16:76].decode('utf-16-le').strip('\x00')
run_count = struct.unpack('<I', data[208:212])[0] if version >= 23 else struct.unpack('<I', data[144:148])[0]
result = {
'version': version,
'executable': exec_name,
'file_size': file_size,
'run_count': run_count,
}
# Extract last execution timestampsif version == 23: # Vista/7 - 1 timestamp
ts = struct.unpack('<Q', data[128:136])[0]
result['last_run'] = filetime_to_datetime(ts)
elif version >= 26: # Win8+ - up to 8 timestamps
timestamps = []
for i in range(8):
ts = struct.unpack('<Q', data[128+i*8:136+i*8])[0]
if ts > 0:
timestamps.append(filetime_to_datetime(ts))
result['last_run_times'] = timestamps
return result
def filetime_to_datetime(ft):
"""Convert Windows FILETIME to datetime string."""if ft == 0:
return None
timestamp = (ft - 116444736000000000) / 10000000
try:
return datetime.utcfromtimestamp(timestamp).strftime('%Y-%m-%d %H:%M:%S UTC')
except (OSError, ValueError):
return None
# Process all prefetch files
prefetch_dir = '/cases/case-2024-001/prefetch/'
results = []
for filename in sorted(os.listdir(prefetch_dir)):
if filename.lower().endswith('.pf'):
filepath = os.path.join(prefetch_dir, filename)
print(f"\n=== {filename} ===")
result = parse_prefetch(filepath)
if result:
print(f" Executable: {result['executable']}")
print(f" Run Count: {result['run_count']}")
if'last_run'in result:
print(f" Last Run: {result['last_run']}")
elif'last_run_times'in result:
for i, ts in enumerate(result['last_run_times']):
print(f" Run Time {i+1}: {ts}")
results.append(result)
# Save results
with open('/cases/case-2024-001/analysis/prefetch_analysis.json', 'w') as f:
json.dump(results, f, indent=2)
PYEOF
Step 4: Identify Suspicious Execution Evidence
# Search for known malicious tool names in prefetchls /cases/case-2024-001/prefetch/ | grep -iE \
'(MIMIKATZ|PSEXEC|WMIC|COBALT|BEACON|PWDUMP|PROCDUMP|LAZAGNE|RUBEUS|BLOODHOUND|SHARPHOUND|CERTUTIL|BITSADMIN)'# Search for script interpreters (potential malicious execution)ls /cases/case-2024-001/prefetch/ | grep -iE \
'(POWERSHELL|CMD\.EXE|WSCRIPT|CSCRIPT|MSHTA|REGSVR32|RUNDLL32|MSIEXEC)'# Search for remote access toolsls /cases/case-2024-001/prefetch/ | grep -iE \
'(TEAMVIEWER|ANYDESK|LOGMEIN|VNC|SPLASHTOP|SCREENCONNECT|AMMYY)'# Search for data exfiltration toolsls /cases/case-2024-001/prefetch/ | grep -iE \
'(RAR|7Z|ZIP|RCLONE|MEGA|DROPBOX|ONEDRIVE|GDRIVE|FTP|CURL|WGET)'# Find recently created prefetch files (newest executables run)ls -lt /cases/case-2024-001/prefetch/ | head -20
# Cross-reference with Shimcache and Amcache for confirmation# Prefetch existence = program was executed at least once
Step 5: Build Execution Timeline
# Create timeline from prefetch data
python3 << 'PYEOF'
import json
import csv
with open('/cases/case-2024-001/analysis/prefetch_analysis.json') as f:
data = json.load(f)
timeline = []
for entry in data:
if'last_run_times'in entry:
for ts in entry['last_run_times']:
if ts:
timeline.append({
'timestamp': ts,
'executable': entry['executable'],
'run_count': entry['run_count'],
'source': 'Prefetch'
})
elif'last_run'in entry and entry['last_run']:
timeline.append({
'timestamp': entry['last_run'],
'executable': entry['executable'],
'run_count': entry['run_count'],
'source': 'Prefetch'
})
# Sort chronologically
timeline.sort(key=lambda x: x['timestamp'])
# Write timeline CSV
with open('/cases/case-2024-001/analysis/execution_timeline.csv', 'w', newline='') as f:
writer = csv.DictWriter(f, fieldnames=['timestamp', 'executable', 'run_count', 'source'])
writer.writeheader()
writer.writerows(timeline)
# Print suspicious time windowfor entry in timeline:
if'2024-01-15'in entry['timestamp'] or '2024-01-16'in entry['timestamp']:
print(f" {entry['timestamp']} | {entry['executable']} (x{entry['run_count']})")
PYEOF
Key Concepts
Concept
Description
Prefetch
Windows performance optimization that pre-loads application data and tracks execution
SCCA signature
Magic bytes identifying a valid Prefetch file
Path hash
CRC-based hash of the executable path forming part of the .pf filename
Run count
Number of times the executable has been launched (may wrap around)
Last run timestamps
Windows 8+ stores up to 8 most recent execution timestamps
Referenced files
List of files and directories accessed during the first 10 seconds of execution
Volume information
Drive serial number and creation date identifying the source volume
MAM compression
Windows 10 Prefetch files use MAM4 compression requiring decompression before parsing
Tools & Systems
Tool
Purpose
PECmd
Eric Zimmerman's Prefetch parser with CSV/JSON output
WinPrefetchView
NirSoft GUI tool for viewing Prefetch files
python-prefetch
Python library for parsing Prefetch files
Prefetch Hash Calculator
Tool to calculate expected hash from executable paths
KAPE
Automated artifact collection including Prefetch
Autopsy
Forensic platform with Prefetch analysis module
Plaso/log2timeline
Super-timeline tool that includes Prefetch parser
Velociraptor
Endpoint agent with Prefetch collection and analysis artifacts
Common Scenarios
Scenario 1: Confirming Malware Execution
Search Prefetch directory for the malware executable name, confirm execution via Prefetch existence, extract run count and last run time, identify referenced DLLs to understand malware behavior, correlate with registry autorun entries.
Scenario 2: Attacker Tool Usage Timeline
Identify Prefetch files for PsExec, Mimikatz, BloodHound, and other attacker tools, build chronological timeline of tool execution, determine the sequence of the attack (reconnaissance, credential theft, lateral movement), match timestamps with network connection logs.
Scenario 3: Data Staging and Exfiltration
Look for Prefetch entries of compression tools (7z, WinRAR, zip), identify execution of file transfer utilities (rclone, FTP clients), check for cloud storage client execution, timeline when data staging and transfer occurred.
Scenario 4: Anti-Forensics Detection
Check for execution of known anti-forensic tools (CCleaner, Eraser, SDelete), identify if Prefetch directory was recently cleared (fewer files than expected for active system), note timestamps of anti-forensic tool execution relative to other evidence.
Output Format
Prefetch Analysis Summary:
System: Windows 10 Pro (Build 19041)
Prefetch Files: 234
Analysis Period: All available execution history
Execution Statistics:
Total unique executables: 234
First execution: 2023-06-15 (system install)
Latest execution: 2024-01-18 23:45 UTC
Suspicious Executions:
MIMIKATZ.EXE-5F2A3B1C.pf
Run Count: 3 | Last: 2024-01-16 02:30:15 UTC
PSEXEC.EXE-AD70946C.pf
Run Count: 7 | Last: 2024-01-16 02:45:30 UTC
RCLONE.EXE-1F3E5A2B.pf
Run Count: 2 | Last: 2024-01-17 03:15:00 UTC
POWERSHELL.EXE-022A1004.pf
Run Count: 145 | Last: 2024-01-18 14:00:00 UTC
Attack Timeline (from Prefetch):
2024-01-15 14:32 - POWERSHELL.EXE (initial access)
2024-01-16 02:30 - MIMIKATZ.EXE (credential theft)
2024-01-16 02:45 - PSEXEC.EXE (lateral movement)
2024-01-17 03:15 - RCLONE.EXE (data exfiltration)
Report: /cases/case-2024-001/analysis/execution_timeline.csv
