Blue Locker Ransomware Dissection

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The “Blue Locker” ransomware  is a sophisticated ransomware strain actively targeting critical sectors such as the oil and gas industry, particularly noted in Pakistan.

Here are the key points about Blue Locker ransomware:

• Infection & Distribution: Blue Locker spreads via phishing emails with malicious attachments or links, drive-by downloads, insecure remote access, and can propagate through local networks and removable devices.
• Behavior: It encrypts files by appending “.blue” or “.bulock16” extensions and leaves ransom notes (often named HOW_TO_BACK_FILES.html or restore_file.txt) that demand payment and sometimes threaten data leakage if ransom is not paid.
• Technical Aspects:
  • Uses a PowerShell-based loader for delivery.
  • Attempts to disable security defenses and escalate privileges.
  • Achieves persistence by inserting itself into Windows Registry autorun keys.
  • Deletes shadow copies to prevent recovery.
  • Uses AES and RSA encryption algorithms.
  • Skips certain system-critical folders and extensions to avoid system instability.
  • Employs obfuscation and anti-analysis techniques.
  • Seeks and terminates browser processes (e.g., Chrome) to encrypt password-related files.
• Targets: Initially identified attacking Pakistani government ministries and the oil and gas sector, but its approach aligns with tactics used by other ransomware aimed at critical infrastructure worldwide.
• Connection to Other Malware: Blue Locker is related to or based on the “Shinra” ransomware family, which may have links to Asia or Iran, with possible false-flag techniques to confuse attribution.
• Response and Alerts: Pakistan’s National Computer Emergency Response Team (CERT) issued warnings to ministries about this threat, emphasizing the need for proactive defensive measures.
• Detection & Mitigation:
  • Detection is possible with current antivirus solutions.
  • Decryption without attackers’ keys is generally not possible.
  • Organizations are urged to maintain regular backups, implement patch management, monitor networks for suspicious activity, and strengthen cybersecurity hygiene.
• Ransom Note and Communication: The attackers provide contact options through ProtonMail, Jabber IM, and TOX IM for ransom negotiations.
• Impact: Blue Locker ransomware is regarded as a significant threat due to its encryption capabilities combined with potential data exfiltration and double extortion tactics requiring urgent and layered security responses.

For cybersecurity professionals, understanding Blue Locker’s behavior, IoCs, and attack methods is vital for prevention and incident response planning, especially for organizations in highly targeted sectors and regions.

Blue Locker Attack Techniques

Initial Access:

• Delivered mainly via targeted phishing emails with malicious attachments or links.
• Uses social engineering to trick victims into executing the malware.

Persistence:

• Achieves persistence by adding itself to Registry Run Keys under:
  HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Run
• Modifies system services for privilege escalation.
• Bypasses User Account Control (UAC) through registry manipulation to elevate privileges silently.

Execution:

• Executes payload silently and deploys ransomware using native Windows API calls.
• Terminates specific processes (e.g., Chrome.exe) forcibly to access locked files like password databases.

Encryption:

• Uses a combination of AES and RSA encryption algorithms.
• Encrypts various file types but excludes certain system-critical folders and file extensions such as .cat, .bat, .cmd, .ps1, and .vbs.
• Appends encrypted files with the .Blue extension.
• Deletes shadow copies using WMIC command to prevent file recovery:
  wmic SHADOWCOPY DELETE

Defense Evasion:

• Uses obfuscation and deobfuscation techniques to evade antivirus detection.
• Alters file timestamps (timestomping) to complicate forensic analysis.
• Detects and avoids virtualized or sandbox environments.
• Disables UAC to avoid interruption by security controls.

Discovery and Credential Access:

• Enumerates running processes, user accounts, and installed software.
• Searches for specific encoded strings to identify and terminate targeted processes.
• Harvests credentials by terminating browser processes and encrypting password-related files.

Impact:

• Stops critical system services to avoid interruption of encryption.
• Deletes backups and shadow copies to hinder recovery, ensuring maximum damage.

Indicators of Compromise (IoCs)

• File extensions appended: .Blue
• Ransom note filename: restore_file.txt
• Unique obfuscated string used in memory: XOR-encoded variant of “Chrome.exe” (displayed as Chinese-like characters)
• Registry key for persistence:
  HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Run
• Known file hashes related to Blue Locker samples:
• d3cc6cc4538d57f2d1f8a9d46a3e8be73ed849f7fe37d1d969c0377cf1d0fadc
• e6bd4ed287d1336206f5b4b65011e570267418799eb60c2d0d7496d5d9e95a33
• 6eeb20cc709a18bf8845f7b678967b7f0ff96475cf51a261da87244886bbfd2e
• 515bd71a8b3c2bce7b40b89ddfe2e94d332b0779d569c58117f8dcdcb8a91ed9
• Communication channels listed in ransom note:
• ProtonMail: hyebwma@protonmail.com
• Jabber IM: hsbwabwy@xmpp.jp
• TOX IM account for anonymous communication