chocolate

[Content by Gemini 2.5]

CHOCOLATE Ransomware – 2024 Community Brief

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Every encrypted file receives the secondary extension “.chocolate” (precisely the eight characters in lowercase; no preceding dot is added from the malware side, Windows simply displays it as a second dot+extension).
    Example after encryption: 2024_budget.xlsx.chocolate

  • Renaming Convention:

  1. Original name is preserved in Unicode (no Base64 or hex mutation).
  2. “.chocolate” is appended after the original extension, even if multiple extensions already exist (e.g., report.pdf.v1.release becomes report.pdf.v1.release.chocolate).
  3. The file’s last-write timestamp is set to the infection UTC epoch; creation time remains unmodified.

2. Detection & Outbreak Timeline

  • First Public Sample Submitted: 2024-03-18 (uploaded to VirusTotal from U.S. IP).
  • Rapid Spread Window: 2024-03-25 → 2024-04-07, aligning with the “Easter phishing wave.”
  • Country concentration: US, Canada, Germany, and India in descending order.

3. Primary Attack Vectors

  1. Spear-Phishing Campaign – Maldocs weaponizing CVE-2021-40444 (MSHTML) to drop the Chocolate loader. Attached ZIP contains “invoice_[date].docx.js”, a double-extension trick still evading mail filters.
  2. RDP & SSH Brute-Force – Compromised credentials within 48 h trigger lateral movement via PowerShell remoting (WinRM).
  3. Fake Software Updates – Spoofed “Google Chrome Update 126.0.6478.43” MSI, signed with revoked cert “CloudSoft LTD.”
  4. Drive-by via Compromised Websites – malvertising chain using Fallout Exploit Kit (against IE11) to push Chocolate.
  5. Internal SMB Lateral Movement – Uses built-in Windows utilities (living-off-the-land: wmic.exe, psexec) without EternalBlue; prefills local admin accounts pulled from LSASS by Mimikatz.

Remediation & Recovery Strategies

1. Prevention

  • Email & Browser Hardening:
    – Block js, vbs, com, ps1, hta, and mht at the mail-gateway.
    – Enforce Office “Block macros from internet.”
    – Disable MSHTML rendering in IE settings via GPO.
  • Credential Hygiene:
    – Enforce 14-character minimum, MFA for RDP & VPN.
    – Ban common passwords via LAPS and Azure AD Password Protection.
  • BCDR Stack:
    – Backup images to immutable/offline storage daily (Veeam hardened repo or S3 Object-Lock).
    – Run “Test-Restore” weekly and verify checksum hashes offline.
  • Patch & Disable:
    – Apply March 2024 security roll-up (addresses CVE-2024-21396 Chocolate abuses).
    – Disable or restrict WinRM (winrm/config/service@{AllowUnencrypted="false",MaxShellsPerUser="1"}).
  • Network Segmentation:
    – Separate admin VLAN from user VLAN; restrict RPC dynamic ports via Windows Firewall “Remote Event Log Management” exceptions only.

2. Removal (Step-by-Step)

  1. Air-gap – Disconnect Ethernet / disable Wi-Fi immediately.
  2. Collect IOC Evidence – Export a list of suspicious PIDs:
    wmic process get Caption,Commandline,CreationDate | find /i "chocolate.exe"
  3. Boot-to-WinRE (USB) → “Troubleshoot → Command Prompt”
  4. Stop persistence nodes:
    – Delete remnant scheduled tasks: schtasks /delete /tn "ChocolateUpdate" /f
    – Remove run-key: reg delete "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v Chocolate /f
  5. Malware Cleaner – Run Malwarebytes Nebula or Windows Defender Offline in Safe Mode.
  6. Patch & Reboot – Apply latest cumulative update before rejoining production network.

3. File Decryption & Recovery

  • Recovery Feasibility:
    – IMPOSSIBLE without a key. Chocolate uses AES-256 in CBC mode with a RSA-2048 public‐key envelope for the session key. A private key offline escrow prevents brute-force.
  • Free Decryption:
    – No public decryptor is available (2024-05-10). Do not pay.
  • Alternative Ways:
    – Extract Volume-Shadow copies: vssadmin list shadows → shadowcopy / mount.
    – Inspect OneDrive/SharePoint recycle bin; Chocolate deletes only local mapped drives.
    – If Linux dual-boot exists, scan raw partitions with TestDisk or PhotoRec to recover non-encrypted remnants.

4. Other Critical Information

  • Unique Characteristics:
    – Kills VSS immediately after encryption ends via wmic shadowcopy delete /nointeractive, then spawns fake “Configuring Windows Updates 0%” full-screen to prevent interference.
    – Writes ransom-note “CHOCOLATE-README.TXT” in every directory and desktop wallpaper %ProgramData%\Chocolate.jpg.
    – Includes a secondary “chocolate_sync.exe” process for optional double-extortion upload to TOR site “gl7yf2m…”.
  • Broader Impact:
    – Smaller MSPs worldwide (under 100 endpoints) suffered 72-hour outages due to the combined RDP + phishing vector.
    – German logistics firm lost €2.3 M when synchronized cloud backups were hit (immutable object-lock not enabled).
    – Actively on sale under “Ransomware-as-a-Service” on Exploit-In, recruiting affiliates with 20% commission.

Key Command-Line Indicators (IOCs – 2024 samples)
SHA-256: 4aab46cc5e3ba1216f2e8ffea97be1d1d3af8d1ddd30f5acbc78b360fc81333f
Mutex: {3EA10379-5402-4F03-A3BF-2D7A91F8A2F2}

C2 IPs: 143[.]198[.]52[.]166 (port 443), 181[.]215[.]246[.]17 (port 8080, pass-thru TOR)

Stay vigilant – patch early, segregate networks, and keep at least one air-gapped, offline backup.