browec

[Content by Gemini 2.5]

The Browec Ransomware Analysis & Response Guide

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The Browec ransomware appends the .browec extension to every encrypted file.
  • Renaming Convention: Files are renamed according to the pattern: [original filename].[original extension].browec
    Example: Document.docx becomes Document.docx.browec

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First observed in widespread circulation during April 2019, with peak activity continuing through mid-2019.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Remote Desktop Protocol (RDP) exploits: Primary vector – attackers target poorly secured or exposed RDP ports (3389) using brute-force attacks, weak credentials, or exploiting BlueKeep vulnerability (CVE-2019-0708).
  • Phishing campaigns with weaponized attachments: Malicious MS Office macros (.docm, .xlsm) and PDF exploit kits.
  • Software supply chain attacks: Compromised legitimate software installers distributed through third-party download sites.
  • EternalBlue exploitation: Older Windows systems still vulnerable to MS17-010 EternalBlue exploit.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  • Immediate RDP hardening:
    • Disable RDP on systems where not required
    • Use VPN access for necessary remote connections
    • Implement IP whitelisting and account lockout policies
    • Change default port from 3389 (security through obscurity layer)
  • Credential security:
    • Enforce 14+ character complex passwords
    • Enable multi-factor authentication (MFA) on all remote access points
    • Disable local administrator accounts and use least-privilege principles
  • Patch management:
    • Apply Windows patches immediately – particularly MS17-010 and KB4499175 (BlueKeep fix)
    • Update third-party applications (Java, Flash, Adobe products)
  • Email security:
    • Disable macro execution from internet-originated documents
    • Implement advanced email filtering with sandboxing capabilities
  • Network segmentation: Isolate critical systems and implement zero-trust architecture

2. Removal

  • Infection Cleanup:
  1. Isolate infected systems: Disconnect from network immediately (pull Ethernet cable/disable Wi-Fi)
  2. Boot into Safe Mode: Restart → F8 (Windows 7) or Shift+Restart → Troubleshoot → Advanced → Startup Settings → Safe Mode with Networking (Windows 10/11)
  3. Terminate malicious processes using Task Manager: Look for suspicious executables (random character names in %TEMP% or %APPDATA%)
  4. Manual removal (if restore unavailable):
    • Delete from Registry: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run – remove entries matching ransomware executables
    • Clean %TEMP% directory: C:\Users\[Username]\AppData\Local\Temp
  5. Automated removal tools:
    • Run Malwarebytes Anti-Ransomware or Bitdefender Anti-Ransomware Tool
    • Perform full scan with reputable antivirus (Kaspersky TDSSKiller, Sophos Intercept X)
  6. Clear restore points: Ransomware frequently corrupts system restore – create new clean restore point post-cleanup

3. File Decryption & Recovery

  • Recovery Feasibility:

  • No decryption possible at this time – Browec uses RSA encryption keys unique per victim

  • Recovery options available:

    • Shadow copies: Check vssadmin list shadows in elevated command prompt – if untouched, restore via:
      vssadmin list shadows
  mklink /d c:\shadowcopy \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy[number]
    • File recovery tools: Recuva, EaseUS Data Recovery Wizard, Stellar Data Recovery
    • Offline backups: Verify backup integrity and restore from most recent clean backup
    • Decryption myth clarification: No known master decryption keys exist – avoid any websites claiming “free browec decryptor”

  • Essential Tools/Patches:

  • Prevention patches:

    • Microsoft KB4499175 (BlueKeep patch)
    • KB4012598 (EternalBlue patch for legacy Windows)
    • Windows Defender updates KB2267602

  • Detection tools:

    • Microsoft Enhanced Mitigation Experience Toolkit (EMET)
    • Sysinternals Process Explorer for real-time monitoring
    • Wireshark for network anomaly detection

  • Recovery utilities:

    • Windows Recovery Environment (WinRE) bootable USB
    • Clonezilla for bit-for-bit disk imaging before recovery attempts

4. Other Critical Information

  • Additional Precautions:

  • Fast encryption behavior: Encrypts local files first, then network shares – time to full encryption: 15-45 minutes

  • Persistence mechanisms: Creates Windows service named “BROEXT” and copies itself to %WINDIR%\System32\ as random-named executable

  • Information stealing component: Also exfiltrates browser credentials and cryptocurrency wallet data

  • Ransom note locations: Drops “_readme.txt” in every encrypted directory

  • Payment verification: Criminals use TOR sites – NEVER negotiate or pay ransom

  • Broader Impact:

  • Industry targeting: Predominantly affects manufacturing, logistics, and medical practices (high-value RDP targets)

  • Geographic spread: Most active in North America and Western Europe

  • Economic impact: Average ransom demand of $980 (reduced to $490 if paid within 72 hours)

  • Clean-up time: Average incident response time 3-5 days for businesses with proper planning

  • Insurance implications: Many cybersecurity insurance policies exclude coverage for RDP-based attacks

Emergency Response Checklist:

  1. DO NOT restart infected systems – this may trigger additional encryption rounds
  2. Photograph ransom note for incident documentation
  3. Contact local cyber-crime authorities (FBI Internet Crime Complaint Center for US: ic3.gov)
  4. Begin incident response following established protocols
  5. Document everything for potential legal proceedings