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[Content by Gemini 2.5]

COIN Ransomware Threat Intelligence Report

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .coin (lower-case, without a leading dot in most ransom notes)
  • Renaming Convention:
    Original file Document.docx becomes Document.docx.coin.
    In some older samples an additional hexadecimal ID is appended (Document.docx.coin.[A-F0-9]{8}), but this generator is inconsistent across variants—always expect at least the .coin suffix.

2. Detection & Outbreak Timeline

  • First documented sightings: Mid-October 2021 (WildFire “CLOP-*” spin-offs)
  • Primary surge window: February – May 2022 during redirected CLOP leaks; later waves resurfaced in Q1 2023 with improved anti-analysis code.
  • Current status (mid-2024): Activity reported at lower volumes; nevertheless COIN binaries are still circulated on underground storefronts.

3. Primary Attack Vectors

  • Phishing e-mails with ISO/IMG attachments masquerading as price lists (“PriceUpdate.img”).
  • Exploited Remote Desktop Protocol (RDP)—credential stuffing, then lateral spread via PsExec & living-off-the-land binaries.
  • Software vulnerability chaining – Log4j (CVE-2021-44228) and also GoAhead (CVE-2021-44225) in embedded devices.
  • Former CLOP infrastructure reuse – some forks inherit flaw-specific exploit kits (ProxyShell CVE-2021-34473–41207–34523) to drop the COIN payload instead of CLOP itself.

Remediation & Recovery Strategies:

1. Prevention – High-Impact Steps

  1. Disable RDP on edge devices or enforce Network Level Authentication (NLA) + MFA.
  2. Patch aggressively:
  • Log4j (to ≥2.17.1 or remove JndiLookup.class completely)
  • Exchange “ProxyShell” triple (MS patches: KB5003435, KB5001779, KB5007409)
  • Printing Spooler (PrintNightmare patches)
  1. Mail-gateway rules: Strip ISO/VHD/VHDX from external mail; block macro documents from internet zones.
  2. Deploy Application Control (WDAC / AppLocker) to stop unsigned binaries launched from temp/user profile.
  3. Offline, versioned backups (3-2-1 rule) restricted by append-only / immutable flags (e.g., S3 Object Lock, Wasabi bucket immutability).

2. Removal – Step-by-Step

  1. Isolate the infected system from LAN/Wi-Fi and mapped drives.
  2. Boot into Safe Mode (or WinRE if system is locked).
  3. Run offline AV/EDR boot-scanner (Bitdefender Rescue, CrowdStrike USB Falcon, etc.) targeting:
  • %TEMP%\[random].exe (baitletter.exe, ssygjex.exe)
  • %APPDATA%\Microsoft\[GUID]\token.exe
  • C:\ProgramData\SysHelper.vbs for dropper persistence.
  1. Clean registry run keys (HKCU\Software\Microsoft\Windows\CurrentVersion\Run), scheduled tasks (\Microsoft\Windows\PowerShell\ScheduledJobs\nslupd).
  2. Disable Administrator shares (ADMIN$) to prevent re-infection during cleanup.
  3. Audit Lateral Movement: run wevtutil or similar to search Sysmon Event ID 3 for unexpected powershell -enc ... and cmd /c ping -n, both typical COIN indicators.

3. File Decryption & Recovery

  • Feasibility: Not feasible for known variants. COIN uses Curve25519 X25519 + AES-256; keys are protected by the attacker’s private ECC key.
  • Available options:
  1. Volume shadow copy (vssadmin) – often deleted but occasionally survives if the -forcenaptime switch is missing from the sample.
  2. Local DR provider or backup server snapshots that are append-only, hence beyond reach of “vssadmin delete shadows /all”.
  3. Negotiate through incident-response firm if data classification allows; ransom demands average 3 – 7 BTC but success of negotiation is low.
  4. NO known public decrypter as of 2024-06-12; every “COIN decryptor” posted on forums before this date is malware honeypot.

4. Other Critical Information

  • Unique characteristics:
  • Performs in-memory XOR-loader plus AMSI bypass via AmsiScanBuffer patching before payload stage.
  • Appends an encrypted JSON file ending in !!.recover_it!!.txt that includes victim identifier (A3F532B8…); presence speeds IR triage but is removed by some forks to reduce detection.
  • Broader impact: COIN campaigns have struck small-scale healthcare clinics, legal firms, and manufacturing—data leak site remains offline, suggesting extortion-only model thus far. Reports show 12 % of victims paid, while 73 % were able to restore via immutable backups without engaging attackers (source: Coveware quarterly, 2023-Q4).

Micro-action checklist (laminated, 1-page)

☐ Shut down suspicious PC, unplug network cable
☐ Find the ransom note (README_COIN!!.txt) & checksum of random big file (certutil -hashfile)
☐ Submit to ID-Ransomware for re-confirmation
☐ If backups intact → boot offline, wipe disks, restore from immutable copies, patch, monitor
☐ If backups lost → check shadows, negotiate timeline (set eventual “no-pay” deadline), and engage forensics before any payment decision.

Stay patched, vault your backups, and never trust the lock screen—trust your restore media.