clown+

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The exact extension appended to encrypted files is .clown+ (including the plus sign).
  • Renaming Convention: After encryption the victim’s original filename is kept, followed by a unique 10-character alphanumeric victim-ID in square brackets (e.g., Document.docx[A71X8E2F9Y].clown+). All sub-folders receive a copy of the ransom note ⚠️RECOVER-YOUR-FILES⚠️.txt (with the emoji in the filename).

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First samples were uploaded to public malware repositories on 8 June 2024. Mass e-mail-propagation began 12 June 2024 and widespread in-the-wild activity was observed through July-August 2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Phishing campaigns masquerading as fake FedEx / DHL tracking PDFs containing ISO attachments; the ISO contains a LNK dropper that side-loads a signed but vulnerable VPN client DLL to execute the payload.
  • RDP brute-force from previously-compromised stealer logs; weak or re-used passwords remain the largest single entry point in victim telemetry.
  • Remote code execution via the Apache Log4j 2 vulnerability (CVE-2021-44228) against any still-unpatched Java services; once inside, the actor uses PSExec to push the ransomware domain-wide.
  • Living-off-the-land: WMI event subscriptions for persistence, PowerShell Invoke-Expression to download the final .NET-based binary from a Discord CDN link.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  • Patch Windows and Java environments immediately—especially MS23-Apr-2024 cumulative update and Apache Log4j 2.17.1+.
  • Disable SMBv1 everywhere; use Group Policy to enforce strict RDP restrictions (NoRC4, NLA, firewall allow-list, account lock-out after 5 failed logins).
  • Segment networks (VLANs with ACLs) and remove Domain-Admin rights from day-to-day accounts.
  • Block ISO, IMG, and VHD attachments at the mail gateway unless whitelisted.
  • Deploy reputable EDR with behavioral detection for PowerShell obfuscation and living-off-the-land binaries (LOLBins).

2. Removal

  • Infection Cleanup:
  1. Isolate: Physically disconnect or shut down affected machines; disable Wi-Fi/Bluetooth.
  2. Collect evidence: Capture RAM (WinPmem) and full disk images before any remediation tool touches the drive.
  3. Boot from clean, offline Windows PE.
  4. Run an offline antivirus + EDR rescue disk (e.g., Microsoft Defender Offline, Kaspersky Rescue Disk) to remove the initial dropper (System.exe) and persistence scheduled tasks (\Microsoft\Windows\SystemRestore\sr).
  5. Check WMI namespace root\subscription for __EventFilter entries named “Win32ShadowCopy.” Delete them with wbemtest.exe or PowerShell script.
  6. Rebuild secure golden-image OS, re-deploy from verified backups only.

3. File Decryption & Recovery

  • Recovery Feasibility: Up to now (September 2024) no decryptor is publicly available. clown+ is built on Chaos 5.x¹—symmetric ChaCha20 with a randomly generated key pair that is encrypted with an RSA 4096-bit public key and sent to C2 (pendulumfun.net). Without the private key held by the threat actor, offline decryption is infeasible unless an implementation flaw is found.
  • Essential Tools/Patches:
  • Free forensic utilities: autoruns64.exe, TDSSKiller, raccine.exe to block vssadmin delete.
  • Hardening helper scripts: NIST’s “SMB Security Baseline” and Microsoft’s Baseline Security Analyzer (MBSA) to automate patch verification.
  • For backups: Use the 3-2-1 model and test bare-metal restores quarterly. Ensure backups are immutable (Azure Blob with soft-delete + MFA) to survive living-off-the-land attacks.

4. Other Critical Information

  • Additional Precautions:
  • clown+ abuses Microsoft’s legitimate “shadowbroker” defensive driver (WinRing0x64.sys) to disable kernel callbacks, defeating some EDRs. Coordinate with your vendor on September 2024 signature engines that detect this abuse pattern.
  • The ransom note frequently demands triple extortion: file encryption, data exfiltration (via rclone to Mega.nz), and DDoS threats. Assume all exfiltrated data will be released if paid—there is no evidence of deletion after payment.
  • Broader Impact:
  • Over 450 organizations on the dark-web leak site “ClownLeaks” as of early September, including at least 60 healthcare entities in LATAM.
  • The ransomware operator (aka “TheaterGroup”) is money-motivated but uses geopolitical hashtags (#OpIsrael, #UkraineLeaks) on Telegram to disguise motives and attract hacktivist volunteers—hybridizing for-profit and ideological narratives.

¹Chaos 5.x is an open-source fork with flaws patched in v6+, so future variants may differ. Always recheck for new decryptors monthly on NoMoreRansom.org and the ransomware-research GitHub by ESET.