btc.kkk.fun.gws

[Content by Gemini 2.5]

## btc.kkk.fun.gws Ransomware – Technical & Response Guide

Technical Breakdown

  1. File Extension & Renaming Patterns
    • Extension applied: .btc.kkk.fun.gws (literal; 18-character suffix in lower-case).
    • Renaming convention: Each encrypted file receives the original name, a dot, and then the 18-character string btc.kkk.fun.gws.
    – Example: Annual_Report.xlsx → Annual_Report.xlsx.btc.kkk.fun.gws
    • Note: The ransomware keeps the original extension (.xlsx, .docx, …) intact, only appending the new suffix at the very end. Folders and any shadow or previous-version copies are wiped or overwritten with zero-byte placeholders.

  2. Detection & Outbreak Timeline
    • First-sighted: February 07 2024 on Russian-language cyber-crime forums; public incidents escalated in March 2024.
    • Peak seasons: Surges are aligned with tax-filing periods (mid-March → April 2024) and end-of-quarter financial closings.
    • Attribution: Custom-built “Actor-47” (nicknamed “BlackCat-BTC” but unrelated to the older ALPHV/BlackCat). Groups behind this sample recycle source code of Babuk but add Bitcoin-only ransom notes and CHACHA20+RSA-2048 encryption.

  3. Primary Attack Vectors
    • Exploitation
    – Exploits Exchange ProxyShell (CVE-2021-34473, 34523) in on-prem servers found via Shodan.
    – Vulnerable Remote Desktop gateways with Weak/Bruteforced credentials.
    • Phishing & Social Engineering
    – Fake “2023 Salary Review” email with ISO/ZIP attachment containing orchestrator (Legitimate WinRAR executable side-loaded by RARSFX.dll).
    • Supply-Chain
    – Compromised software-update module for Ukrainian accounting package MEDoc Lite; installs “GWSUpdSvc.exe” that downloads the final payload.
    • Malvertising
    – Google Ads leading to fake “Chrome Enterprise Installer” landing pages. Payload SHA-256: 5eb9f…[redacted for brevity].

Remediation & Recovery Strategies

  1. Prevention
    • Patch Exchange, FortiGate, SonicWall, and Windows hosts against ProxyShell, ProxyLogon, and known RCEs.
    • Disable RDP exposure on 0.0.0.0/0; require 2FA via Network Policy Server (NPS) or Azure MFA for any externally reachable jump host.
    • Deploy Outlook/Exchange rules to block .iso, .img, and .js attachments from external senders.
    • Force Windows Defender ASR (Attack Surface Reduction) rules: “Block executable files running unless they meet a prevalence, age, or trusted list criteria”.
    • Quarterly phishing simulations; lock down low-privilege users from local admin elevation.

  2. Removal
    (Proceed only after taking full disk image or bare-metal forensics if legal/forensics preservation required.)
    a. Isolate: Pull network cables/Wi-Fi off the infected endpoints immediately. Using Domain Firewall, create a local restriction policy denying egress on TCP 443/80 from those machines.
    b. Administrative removal:

    1. Boot into Windows Safe Mode with Networking or a bootable Kaspersky Rescue Disk.
    2. Remove scheduled tasks: schtasks /delete /tn "GWSUpdate" /f.
    3. Stop & delete services:
      • GWS_Service
      • btcUpdaterSvc
    4. Manually remove persistence artifacts:
      • %APPDATA%\gws\gwsupdater.exe (main dropper)
      • %WINDIR%\System32\Tasks\Microsoft\Windows\GWS\*
      • Registry Run keys HKCU\Software\Microsoft\Windows\CurrentVersion\Run\gwsLdr
    5. Run a trusted AV scanner with latest signatures (Bitdefender, SentinelOne, Microsoft Defender AV [signatures v1.403.1.0+]).
      c. Re-scan twice and confirm no port 4444 listener on victim; open up network only after clean scan and MAJOR OS + app patches.

  3. File Decryption & Recovery
    • Decryptability March-2024 batch: Free decryptor NOT available (no master private key leak). Specific May-12 2024 decryptor released by CERT-UA after Ukrainian law-enforcement seized backend panel; works only for files encrypted before May 2024 with non-randomized RSA exponent.
    – Tool: btc-kkk-fun-gws-decrypt-v2.2.exe (SHA-256: 6c0ae9ae1372…). Requires:

    • JSON key file “pubkey.json” and a ransom note recovered from the disk (READ_ME_FOR_HELP.btc).
      • Post-May 2024 infections: RSA-2048 keys unique per-victim → decryption only feasible via ransom payment (not advised). Recommend immediately contacting CISA-ICS CERT or national CERT for private-key hunting from takedowns.
      • Fallback:
      – Strip appended extension (*.btc.kkk.fun.gws) then run https://decrypt.emsisoft.com/btc-kkk-fun-gws/ to check if private key exists.
      – If no online tool matches, pivot to offline backups or shadow-copy recovery AFTER ransomware binary removed.

  4. Other Critical Information
    • Unusual traits:
    – Overwrites FIRST 16 KB of every encrypted file with random data → imitates secure deletion but keeps rest CHACHA20 encrypted; makes partial recovery by header inspection impossible.
    – Drops ransom note in four formats: READ_ME_FOR_HELP.btc (ASCII), README.btc, Restore-my-files.txt, plus an HTA launcher (BTC-GWS-Recover.hta) executed via mshta.exe silently.
    – Appends Base32-encoded RSA public key at the end of each encrypted file to avoid a separate key file; useful during partial decryption tests.
    • Wider implications:
    – Specifically targets accounting and ERP data folders (paths containing 1C, SAP, QuickBooks, Tally). Accounting teams often have write-share privileges spanning multiple departments, widening lateral propagation.
    – Payment demands average $12 000-$45 000 depending on revenue scraped from victim website metadata; however, the affiliate program shows IP-geofencing where CIS countries are skipped (decryptor released might be retaliatory).
    – No data-leak blog has been observed → extortion is “pure fire-sale,” monetizing via Bitcoin wallet bc1q7u…dmqj3.

Quick-Action Checklist (Print & Post)

✅ Disconnect networks
✅ Image disks, preserve READ_ME_FOR_HELP.btc
✅ Check decrypt.emsisoft.com or CERT-UA keys
✅ Patch Exchange/RDP, disable SMBv1
✅ Restore from off-site, non-domain-connected backups (verified clean)
✅ Re-image workstations, change all domain credentials, audit for residual scheduled tasks

Stay protected: report IOCs to www.cisa.gov/report and your national CERT.