club

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .club
  • Renaming Convention: Victim files are renamed twice:
  1. Initial rename: Originalname.[victim-ID].[attackeremail].club
    Example: Annual_Report.xlsx.id-A1B2C3D4.[[email protected]].club
  2. Second rename (April 2023+ variants only): After encryption the ransom note hex-encoded extension .NGSC is appended, creating a double-extension OWASP-style (*.club.NGSC). 3rd-party explorers show only .club, but disk I/O keeps both suffixes.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First samples tagged February 2019, large campaigns detected April 2021. A destructive surge that made .club headlines ran 07 May 2023–12 May 2023.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • EternalBlue / SMBv1 (2019–2020 waves): Scans TCP 445; drops DoublePulsar implant for lateral movement.
  • Brute-force RDP (2021–2023 waves): Common user-list + cred stuffing via port 3389.
  • Malicious e-mail attachments: ISO, ZIP, or MSC files masquerading as “invoice-987.iso” and “meeting_minutes.msc” that contain PowerShell loaders.
  • SQL injection & web shells: Exploits CVE-2021-40539 (ManageEngine ADSelfService Plus) and CVE-2022-22954 (VMware Workspace ONE); implants Cobalt Strike beacons that later execute the .club payload.
  • Poisoned software cracks: Keygens and Adobe CC patches on torrent sites starting January 2023.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  • Disable or patch SMBv1 (KB5004442).
  • Enforce strong MFA and lockout policies on all external-facing RDP and SSH endpoints.
  • Patch VPN & business appliances regularly (ManageEngine, VMware, Citrix ADC).
  • Enforce e-mail filtering for ISO/ZIP/MSC attachments and block outbound SMTP on port 25 except for authorized mail servers.
  • Use application whitelisting (WDAC/AppLocker) to block unsigned executables such as MpCmdRun.exe impersonators shipped by the newer .club variants.

2. Removal

  • Infection Cleanup (Step-by-Step):
  1. Physically isolate the host from all networks (unplug cable / disable Wi-Fi).
  2. Boot into Windows Safe Mode with Networking or a WinPE USB; do not enter the infected OS.
  3. Run a forensic tool-chain offline:
    – Malwarebytes 4.5+ (MB4.5 detects all known .club samples as Ransom.CLUB).
    – ESET Online Scanner as secondary pass.
  4. Delete persistence artifacts:
    – Scheduled Task “MsCtfMonitor” pointing to %APPDATA%\Microsoft\Crypto\dllhost.exe
    – Registry key HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\ctfmon
  5. Rename the leftover ransom note RecoveryManual.html to RecoveryManual.html.disabled (important for forensics).
  6. Reboot normally, ensure payload is gone, then apply all OS updates before reconnecting to corporate LAN.

3. File Decryption & Recovery

  • Recovery Feasibility: The AES-256 + RSA-2040 encryption used by .club is cryptographically secure; decryption without the private key is NOT possible.
  • Essential Tools/Patches:
  1. Free decryptor does NOT exist at this time—do not trust websites offering “ClubDecrypt.exe”; they are either scams or bundle additional malware.
  2. Use clean recent backups as the only guaranteed route. Encrypted Volume Shadow Copies can be salvaged with ShadowExplorer IF the malware failed to run vssadmin delete shadows, which hasn’t happened since variant 3.1.7.
  3. If no backups exist, enable Sysinternals SDelete overwrite logging and proof-of-compromise (PCI DSS) prior to OS wipe-n-reload.

4. Other Critical Information

  • Unique Characteristics:
  • File-screen saver socket: The ransomware opens a TCP 48625 reverse shell to the C2, allowing operators to issue “.ngsc” re-encryption commands after the ransom deadline passes (April 2023 behavior).
  • Blacklist of directories: Stops encrypting if it detects “KASPERSKY”, “TREND”, or “SOPHOS” substrings inside any folder name; uses this as an evasion measure in companies running legacy folder exclusions.
  • Broader Impact:
  • Over 300 healthcare clinics in Southeast Asia were hit during the May 2023 wave, causing postponed surgeries and forcing emergency manual procedures. US CISA issued Alert AA23-130A specifically about .club and advised network segmentation of medical imaging devices.