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Labs / Registry Hunter

  • Daily Challenge
  • Released 26 Aug 2025

🔍 Can you uncover the hidden persistence mechanism in this compromised registry?

🛡️ Master professional Windows Registry forensics techniques used by digital investigators
🔎 Learn to identify malicious persistence mechanisms hidden in system registries
💻 Discover how attackers abuse legitimate Windows features for persistence
🎯 Develop essential digital forensics skills for real-world incident response

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Daily Challenge

🔍 Registry Hunter - Complete Digital Forensics Solution

Objective: Analyze the Windows Registry export to identify malicious persistence mechanisms and extract the hidden flag from encoded PowerShell commands.
🔍 Step 1: Understanding Windows Registry Persistence

Windows Registry contains numerous locations where malware can establish persistence. Common persistence locations include:

  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run - Programs that run at user login
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce - Programs that run once at next login
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run - System-wide startup programs
  • Services keys - Windows services that start automatically
  • Scheduled Tasks - Tasks scheduled to run at specific times

In this challenge, we need to examine the registry export for suspicious entries that don't belong to legitimate software.

🔍 Step 2: Initial Registry Analysis

Download and open the registry export file registry_export.reg in a text editor. The file contains several registry keys and values. Look for entries in common persistence locations.

🔍 Step 3: Identifying Suspicious Entries

Analyzing each registry entry for legitimacy:

Legitimate Entries (Run Key)
  • Adobe ARM: Adobe Updater - legitimate software
  • Steam: Gaming platform - legitimate software
  • Skype for Desktop: Microsoft communication app - legitimate
Suspicious Entries
  • SecurityUpdate (Run): Uses svchost.exe but with suspicious parameters
  • SystemMaintenance (RunOnce): PowerShell with encoded command - highly suspicious
🔍 Step 4: Analyzing the Malicious PowerShell Command

The most suspicious entry is in the RunOnce key. Look for PowerShell commands with these characteristics:

Red Flags to Identify:

  • -WindowStyle Hidden: Runs PowerShell without visible window
  • -ExecutionPolicy Bypass: Bypasses PowerShell security policies
  • -EncodedCommand: Executes Base64 encoded PowerShell script
  • RunOnce location: Executes once at next login, then removes itself
🔍 Step 5: Base64 Decoding Process

The encoded command needs to be decoded to reveal its true purpose. Look for the Base64 string after the -EncodedCommand parameter.

Decoding Methods:

Method 1: Online Base64 Decoder
  1. Copy the Base64 string
  2. Use any online Base64 decoder
  3. Paste the string and decode
  4. Review the decoded PowerShell command
Method 2: Command Line
# Linux/macOS:
echo "[BASE64_STRING]" | base64 -d

# Windows PowerShell:
[System.Text.Encoding]::Unicode.GetString([System.Convert]::FromBase64String("[BASE64_STRING]"))
🔍 Step 6: Decoded Command Analysis

When decoded, the Base64 string will reveal a PowerShell command that creates a variable containing the flag.

Analysis of the Decoded Command:

  • The command creates a PowerShell variable named $flag
  • The variable contains a UUID format string
  • This represents the flag for the challenge
  • The attacker likely used this as a way to store or transmit sensitive data
🔍 Step 7: Forensics Implications

This registry entry demonstrates several important forensics concepts:

Attack Techniques Identified:
  • Registry Persistence: Using RunOnce for one-time execution
  • PowerShell Abuse: Leveraging legitimate tools for malicious purposes
  • Encoding Obfuscation: Base64 encoding to hide malicious commands
  • Execution Policy Bypass: Circumventing PowerShell security controls
🔍 Step 8: Professional Forensics Tools

In real-world investigations, forensics professionals would use specialized tools:

Registry Analysis Tools
  • Registry Explorer (Eric Zimmerman)
  • RegRipper
  • Registry Decoder
  • Volatility Framework
PowerShell Analysis
  • PowerShell_ISE
  • PowerShell Logging
  • DeepBlueCLI
  • Revoke-Obfuscation
Encoding Analysis
  • CyberChef
  • Base64 decoders
  • Hex editors
  • Custom Python scripts
🔍 Step 9: Flag Extraction Process

The complete process to extract the flag:

  1. Download: Obtain the registry_export.reg file
  2. Analyze: Examine registry keys for suspicious entries
  3. Identify: Locate the RunOnce key with encoded PowerShell
  4. Extract: Copy the Base64 encoded string
  5. Decode: Use Base64 decoder to reveal PowerShell command
  6. Extract Flag: Identify the UUID in the decoded command variable
Success: The flag will be the UUID value found in the decoded PowerShell variable assignment.
🔍 Step 10: Learning Outcomes

This challenge demonstrates several key forensics concepts:

  • Registry Forensics: Understanding Windows Registry structure and persistence locations
  • Malware Analysis: Identifying suspicious registry entries and encoded commands
  • PowerShell Security: Understanding PowerShell execution policies and bypass techniques
  • Encoding Analysis: Decoding Base64 and other encoding schemes used by attackers
  • Incident Response: Systematic approach to analyzing digital evidence
Real-World Application: These techniques are essential for digital forensics investigators, incident response teams, and malware analysts who need to understand how attackers establish persistence and hide malicious activities in Windows systems.