coin locker - NTAPINSIGHT

Technical Breakdown – “Coin Locker” (.coin)

1. File Extension & Renaming Patterns

Confirmation of File Extension: The ransomware consistently appends .coin to every encrypted file.
Example: Project_Q2_budget.xlsx → Project_Q2_budget.xlsx.coin
Renaming Convention:
– Encrypted folders remain in their original tree structure; only the leaf filename is altered.
– Long directory paths are NOT truncated or randomized, which helps when validating backups.
– No prepended ID tokens (distinct from Dharma/Phobos families).

2. Detection & Outbreak Timeline

Approximate Start Date/Period:
– Original campaigns surfaced December 2022 on dark-web markets.
– First laboratory samples reverse-engineered by researchers February 2023 (VMRay, Any.Run).
– Mass spam wave leveraging QakBot loader observed April–June 2023.

3. Primary Attack Vectors

| Mechanism | Details & Exploit Paths |
|———–|————————-|
| Phishing (leading vector) | ZIP, ISO, or IMG lures that launch a PowerShell stager → dropping Cobalt Strike → manual Coin Locker deployment. |
| External-Facing RDP (Port 3389) | Brute-force + credential stuffing → disables Windows Defender via WMI → uploads coin.exe from C2. |
| SMBv1 / EternalBlue | Still abused on unpatched devices; the ransomware itself does not exploit SMB, but earlier loaders do. |
| Software Supply-Chain | Fake MSI installers for well-known utilities (e.g., uTorrent, Notepad++) hosted on look-alike domains. |

Remediation & Recovery Strategies

1. Prevention

Patch aggressively:
– Disable SMBv1 (KB2696547, PowerShell: Disable-WindowsOptionalFeature ‑Online ‑FeatureName SMB1Protocol).
– Apply latest Remote Desktop Services (KB5022282 / KB5025221) for Jan 2023+ mitigations.
Email & Web filtering:
– Block ISO/IMG extensions at the perimeter.
– Configure GPO to prevent Office macros from the Internet.
Implement EDR & Credential Hygiene:
– Least-Privilege AD + MFA for privileged accounts.
– Mandate 14-character unique passwords on exposed RDP hosts (NIST SP 800-63B).

2. Removal

| Step | Action |
|——|——–|
| 1. Isolate | Immediately disconnect host from network; disable Wi-Fi and Bluetooth. |
| 2. Identify persistence | Review registry HKCU\Software\Microsoft\Windows\CurrentVersion\Run, scheduled tasks, and Autoruns64.exe. |
| 3. Kill active payloads | Use RKill to terminate malicious processes before scanning. |
| 4. AV scan | Run ESET Online Scanner, Malwarebytes, or Microsoft Defender Offline. |
| 5. Manual clean-up | Delete %APPDATA%\CoinLocker\, remove malicious services (sc delete “coinsvc”). |
| 6. Validate IOCs (MD5) 11c7f4a4e6…d432, Mutex string: {F1C8C2A9-1BC2-4E6A-94F7-3AB1F5C0F698} |

3. File Decryption & Recovery

Recovery Feasibility:
– Free decryptor is available for Coin Locker versions ≤v2.1 released by ’CoinUnlocker Team’ (April 2023).
– Victims with the later v3.0+ build must rely on backups; there is no public decryptor; ransom demands are usually 0.15 BTC, negotiable.

Essential Tools & Patches:

Emsisoft Emergency Toolkit (v2023.2) – Bootable ISO for offline scans.
Microsoft MSERT – on-demand Microsoft Safety Scanner.
Veeam Recovery Media (or equivalent offline images) for complete bare-metal restores.
Whitelisting run-script from Windows 10/11 v22H2 that blocks unsigned executables running from “%APPDATA%*” locations.

4. Other Critical Information

Unique traits vs. peers:
– Coin Locker pre-encrypts VSS snapshots via vssadmin delete shadows /all /quiet within the first 30 seconds of execution—faster than most families.
– Leverages Windows Restart Manager to close Office/Outlook handles cleanly, ensuring maximum file damage.
Broader impact:
– According to the insurance company Coalition’s 2023 Cyber Claims Report, Coin Locker toppled 307 SMEs in North America alone, with an average extortion demand of $1.1 M USD.
– A major eye-care provider leaked PHI when its file share was encrypted; OCR later fined the company $4.5 M under HIPAA.