Anti Forensic Detection

Anti-Forensic Detection and Investigation

This skill helps security professionals detect and investigate anti-forensic techniques that attackers use to evade detection. It covers Windows and Linux systems, focusing on identifying tampering rather than performing it.

Investigation Workflow

1. Gather evidence - Collect relevant artifacts (disk images, memory dumps, logs)
2. Identify anomalies - Look for mismatches, gaps, and suspicious patterns
3. Correlate findings - Cross-reference multiple data sources
4. Document timeline - Reconstruct events despite tampering attempts

Timestamp Manipulation Detection

NTFS Timestamp Analysis

Attackers often modify file timestamps to hide their activity. Detect this by:

Check for MACE attribute mismatches:

• $STANDARD_INFORMATION vs $FILE_NAME timestamps should match
• Tools like TimeStomp only modify $STANDARD_INFORMATION, leaving $FILE_NAME unchanged
• Use forensic tools to compare both attributes

Look for suspicious timestamp precision:

• NTFS timestamps have 100-nanosecond precision
• Round timestamps (e.g., 2010-10-10 10:10:00.00000000) are highly suspicious
• Attackers often set clean, round times that don't occur naturally

Investigation commands:

# PowerShell - Check file timestamps
Get-Item "C:\path\to\file" | Select-Object Name, CreationTime, LastWriteTime, LastAccessTime

# Look for files with suspiciously round timestamps
Get-ChildItem -Recurse | Where-Object { $_.LastWriteTime.Second -eq 0 -and $_.LastWriteTime.Millisecond -eq 0 }

USN Journal Analysis

The USN Journal tracks all NTFS volume changes and cannot be easily tampered with:

Use UsnJrnl2Csv to examine changes:

# Parse USN Journal (requires admin)
# Download from: https://github.com/jschicht/UsnJrnl2Csv
UsnJrnl2Csv.exe -d C: -o usn_output.csv

What to look for:

• Timestamp modifications recorded in the journal
• File creation/deletion events that don't match current timestamps
• Bulk operations that suggest automated tampering

$LogFile Analysis

The $LogFile contains write-ahead logging of all metadata changes:

Use LogFileParser:

# Download from: https://github.com/jschicht/LogFileParser
LogFileParser.exe -d C: -o logfile_output.csv

Key indicators:

• CTIME: File creation time
• ATIME: File access time
• MTIME: File modification time
• RTIME: MFT registry modification time

Look for entries showing timestamp modifications after the fact.

Data Hiding Detection

Slack Space Analysis

NTFS uses clusters; unused space within a cluster (slack space) can hide data:

Detection methods:

1. Use FTK Imager to extract slack space
2. Analyze $LogFile and $UsnJrnl for evidence of data addition
3. Look for files with unusual cluster allocations

Tools:

• FTK Imager (forensic imaging)
• Slacker (slack space analysis)
• Autopsy (open-source forensic suite)

Alternate Data Streams (ADS)

Attackers hide payloads in ADS to evade traditional scanners:

Detection commands:

# PowerShell - Enumerate all streams
Get-ChildItem -Recurse -Force | Get-Item -Stream * | Select-Object FullName, Stream, Length

# Command line
streams64.exe -s C:\path\to\directory

# Dir with stream listing
dir /R C:\path\to\directory

What to look for:

• Files with streams larger than expected
• Executable content in streams of document files
• Streams with suspicious names (e.g., win32res.dll)

Recovery:

• Copying to FAT/exFAT or via SMB strips ADS
• Use streams64.exe -d to delete streams (forensic cleanup)

Windows Logging Tampering Detection

UserAssist Registry Analysis

UserAssist tracks executable run times:

Registry locations:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\UserAssist

Detection indicators:

• Start_TrackProgs and Start_TrackEnabled set to 0 (disabled)
• Missing or cleared UserAssist subkeys
• Timestamps that don't match other artifacts

Prefetch Analysis

Prefetch stores application execution data:

Detection indicators:

• EnablePrefetcher and EnableSuperfetch set to 0
• Missing .pf files for commonly used applications
• Prefetch files with creation times that don't match execution history

Registry check:

Get-ItemProperty "HKLM:\SYSTEM\CurrentControlSet\Control\SessionManager\Memory Management\PrefetchParameters" | Select-Object EnablePrefetcher, EnableSuperfetch

Last Access Time

Detection:

# Check if last access time is disabled
Get-ItemProperty "HKLM:\SYSTEM\CurrentControlSet\Control\FileSystem" | Select-Object NtfsDisableLastAccessUpdate

Value of 1 means last access time updates are disabled.

USB History Tampering

Registry locations:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USBSTOR

Detection indicators:

• Missing USBSTOR entries when USB devices were used
• setupapi.dev.log in C:\Windows\INF has been deleted or modified
• USBDeview shows gaps in device history

Shadow Copies

Check for shadow copies:

vssadmin list shadowstorage
vssadmin list shadows

Detection indicators:

• Shadow copies deleted (vssadmin delete shadows)
• Volume Shadow Copy service disabled
• Registry key HKLM\SYSTEM\CurrentControlSet\Control\BackupRestore\FilesNotToSnapshot modified

Event Log Tampering

Detection indicators:

• Event logs cleared (check for Event ID 1102 in Security log)
• Event log service disabled
• wevtutil.exe cl or Clear-EventLog commands in PowerShell history

Check for log clearing:

# Look for log clearing events
Get-WinEvent -FilterHashtable @{LogName='Security'; Id=1102} | Select-Object TimeCreated, Message

# Check event log service status
Get-Service -Name EventLog

USN Journal Deletion

Detection:

# Check if USN journal exists
fsutil usn queryjournal D:  # Replace D: with target drive

If the journal is missing or very small, it may have been deleted with:

fsutil usn deletejournal /d C:

Advanced Evasion Detection (2023-2025)

PowerShell ScriptBlock/Module Logging

Detection indicators:

• Registry keys disabled:
  • HKLM:\SOFTWARE\Microsoft\PowerShell\3\PowerShellEngine\EnableScriptBlockLogging
  • HKLM:\SOFTWARE\Policies\Microsoft\Windows\PowerShell\ModuleLogging\EnableModuleLogging
• Event ID 4104/4105/4106 missing from Microsoft-Windows-PowerShell/Operational
• Bulk removal of PowerShell events

Hunting query:

# Check logging status
Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\PowerShell\3\PowerShellEngine" -ErrorAction SilentlyContinue | Select-Object EnableScriptBlockLogging

# Look for PowerShell log clearing
Get-WinEvent -FilterHashtable @{LogName='Microsoft-Windows-PowerShell/Operational'} | Where-Object { $_.Id -eq 4104 } | Measure-Object

ETW Patching Detection

Attackers patch ntdll!EtwEventWrite to suppress EDR events:

Detection methods:

1. Compare ntdll.dll in memory vs. on disk
2. Hook ETW calls before user-mode execution
3. Monitor for WriteProcessMemory to ntdll.dll

Indicators:

• Memory-resident ntdll.dll differs from disk version
• 0xC3 (RET) instruction at EtwEventWrite entry point
• Process-local patches that don't persist across restarts

BYOVD (Bring-Your-Own-Vulnerable-Driver)

Detection indicators:

• Vulnerable signed drivers loaded (e.g., procexp152.sys)
• EDR processes terminated unexpectedly
• Kernel service creation from user-writable paths

Hunting:

# List loaded drivers
Get-WindowsDriver -Online | Select-Object Name, Path, DriverVersion

# Check for vulnerable drivers
Get-Process | Select-Object ProcessName, Id | Where-Object { $_.ProcessName -like "*defender*" -or $_.ProcessName -like "*crowd*" }

Mitigations:

• Enable HVCI/SAC (Hypervisor-Protected Code Integrity)
• Microsoft vulnerable-driver blocklist
• Alert on kernel service creation from suspicious paths

Linux Anti-Forensic Detection

Self-Patching Detection

Attackers patch services to hide exploitation while maintaining access:

Detection methods:

# Debian/Ubuntu - Verify package integrity
dpkg -V activemq

# RHEL/CentOS - Verify package integrity
rpm -Va 'activemq*'

# Find files not owned by package manager
find /opt/activemq/lib -type f -name "*.jar" | while read f; do dpkg -S "$f" 2>/dev/null || echo "Unowned: $f"; done

What to look for:

• JAR/binary versions not matching package manager records
• Symbolic links updated out-of-band
• Files downloaded from artifact repositories (Maven Central, etc.)
• Service restarts without corresponding change management

Timeline analysis:

# Find recently modified files in service directories
find /opt/activemq -type f -printf '%TY-%Tm-%Td %TH:%TM %p\n' | sort

# Look for curl/wget to artifact repositories
grep -r "repo1.maven.org\|jcenter.bintray.com" /var/log/ /root/.bash_history 2>/dev/null

Persistence Detection

Cron/Anacron:

# Check for suspicious cron entries
for d in /etc/cron.*; do [ -f "$d/0anacron" ] && stat -c '%n %y %s' "$d/0anacron"; done

# Search for suspicious commands in cron
grep -R --line-number -E 'curl|wget|python|/bin/sh' /etc/cron.*/* 2>/dev/null

SSH Configuration:

# Check for root login enablement
grep -E '^\s*PermitRootLogin' /etc/ssh/sshd_config

# Check for suspicious shells on system accounts
awk -F: '($7 ~ /bin\/(sh|bash|zsh)/ && $1 ~ /^(games|lp|sync|shutdown|halt|mail|operator)$/) {print}' /etc/passwd

Random beacon artifacts:

# Find short, random-named files
find / -maxdepth 3 -type f -regextype posix-extended -regex '.*/[A-Za-z]{8}$' -exec stat -c '%n %s %y' {} \; 2>/dev/null | sort

Cloud C2 Detection

Dropbox C2 indicators:

• Network: api.dropboxapi.com / content.dropboxapi.com with Bearer tokens
• Hunt in proxy/NetFlow/Zeek/Suricata logs
• Outbound HTTPS to Dropbox from server workloads

Cloudflare Tunnel indicators:

• cloudflared processes or systemd units
• Config files at ~/.cloudflared/*.json
• Outbound 443 to Cloudflare edge IPs

PyInstaller artifacts:

• strings hits: PyInstaller, pyi-archive, PYZ-00.pyz, MEIPASS
• Runtime extraction to /tmp/_MEI* or custom --runtime-tmpdir paths

Investigation Best Practices

Evidence Collection

1. Create forensic images before analysis
2. Calculate hashes (SHA-256) for all evidence
3. Document chain of custody
4. Work on copies, never original evidence

Correlation Strategy

• Cross-reference multiple artifact sources
• Look for inconsistencies between data sources
• Build timeline from multiple independent sources
• Use USN Journal and $LogFile as ground truth for NTFS

Documentation

• Record all commands executed during investigation
• Save tool outputs with timestamps
• Note any anomalies or suspicious findings
• Maintain clear audit trail

Quick Reference Commands

Windows

# Event log clearing detection
Get-WinEvent -FilterHashtable @{LogName='Security'; Id=1102}

# PowerShell logging status
Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\PowerShell\3\PowerShellEngine" | Select-Object EnableScriptBlockLogging

# ADS enumeration
Get-ChildItem -Recurse -Force | Get-Item -Stream *

# Shadow copies
vssadmin list shadows

Linux

# Package integrity
dpkg -V <package>  # Debian
rpm -Va <package>  # RHEL

# Recent file changes
find /path -type f -printf '%TY-%Tm-%Td %TH:%TM %p\n' | sort

# Suspicious cron
grep -r 'curl\|wget\|python' /etc/cron.* 2>/dev/null

# Random artifacts
find / -maxdepth 3 -type f -regex '.*/[A-Za-z]{8}$' 2>/dev/null

References

• Sophos X-Ops – "AuKill: A Weaponized Vulnerable Driver for Disabling EDR" (March 2023)
• Red Canary – "Patching EtwEventWrite for Stealth: Detection & Hunting" (June 2024)
• Red Canary – "Patching for persistence: How DripDropper Linux malware moves through the cloud"
• CVE-2023-46604 – Apache ActiveMQ OpenWire RCE

Tools:

• UsnJrnl2Csv: https://github.com/jschicht/UsnJrnl2Csv
• LogFileParser: https://github.com/jschicht/LogFileParser
• USBDeview: https://www.nirsoft.net/utils/usb_devices_view.html