Comprehensive Analysis & Defense Guide

Ransomware variant: BTCWare

Technical Breakdown:

1. File Extension & Renaming Patterns

Confirmation of File Extension:
BTCWare historically uses an ever-changing set of custom hex-suffix extensions (e.g. .btcware, .cryptobyte, .theva, .onyon, .shadow, .aleta, .nuclear55, .blocking, etc.). Victims will therefore see files such as:
Budget Q3.xlsx.aleta or photo.jpg.shadow.
Renaming Convention:
Original file → [original_filename].[original_extension].[random 4-7-character extension]
The ransomware does not store the original filename inside a renamed wrapper; instead it appends its extension directly, making bulk identification by naming pattern trivial.

2. Detection & Outbreak Timeline

Approximate Start Date/Period:
Initial cluster: March 2017 via spam campaigns against open RDP.
Major wave #1: Late May 2017 (SMB vulnerability intake – similar to WannaCry timeframe).
Major wave #2: July-August 2017 when BTCWare switched to RDP brute-force followed by PsExec lateral movement.
Since then the core code has been forked by multiple actors, giving rise to new “builds” with fresh extensions every 2-3 months.

3. Primary Attack Vectors

Remediation & Recovery Strategies:

1. Prevention

Remote Desktop hardening
Disable RDP unless absolutely required.
If needed: restrict to VPN or IP-whitelisting, enforce strong passwords, enable NLA, block TCP/3389 at perimeter firewalls.
Patching
MS17-010 (SMBv1 vulnerability) – apply immediately or disable SMBv1 entirely.
Any 2017-era Adobe Flash, SilverLight, Office, and Windows updates (KB4012212/KB4012215 for Win7, KB4012598 for legacy systems w/out extended support).
Credential hygiene
Enforce 15-20 character passwords for service accounts.
Use LAPS to randomize local admin passwords.
Audit for reused/domain-privileged accounts on workstations.
Application control & EDR
Windows Defender Application Guard / Windows Defender Anti-ransomware features (controlled folder access).
Sophos Intercept X, CrowdStrike Falcon, or equivalent EDR for behavior-blocking.
Backups
Air-gapped/offline backups with periodic test restores.
Enable versioning on cloud storage (OneDrive, G-Suite); BTCWare unfortunately enumerates and encrypts files synced in real time unless they are versioned/ immutable.

2. Removal

Disconnect from network (wired & Wi-Fi) immediately.
Boot into Safe Mode with Networking.
Identify and kill malicious process(es):

Use Task Manager/Process Explorer; common names: msgpub.exe, unlha32.exe, client.exe, random 7-character EXE located in %APPDATA% or %PROGRAMDATA%.

Clean persistence:

Run Autoruns (Sysinternals) and remove any unknown Services, Run keys, or Scheduled Tasks pointing to the above files.
Check scheduled task name e.g. PowerShell BG service trigger.

Verify removal with a full offline AV/EDR scan (Malwarebytes 4.* definitions detect BTCWare as Ransom.BTCWare).
If lateral movement suspected, re-image the entire subnet / domain controllers.

3. File Decryption & Recovery

Recovery Feasibility:
✅ Partial (historical builds) — Free decryptors exist for many older BTCWare builds (.btcware, .onyon, .shadow, .aleta, .aleta1, .theva, .cry128, .cryptobyte, .taurus, .blocking).
❌ No public decryptor for newer AES-256 or “nuclear” editions (.nuclear55, .mercury extension).
Tools:
Avast BTCWare Decoder (https://www.avast.com/ransomware-decryption-tools#btcware) for legacy variants only. Supply the original file + ransom note.
Bring key.avast.com into EDR console via Boson API to verify platform compatibility.
Recovery Procedure:

Identify exact BTCWare build via ransom note (!#_RESTORE_FILES_#!.inf, DECRYPT-MY-FILES.txt, etc.).
Compare SHA-256 of encrypted file against Avast signature table.
Run decryption tool on a cloned forensics image first — confirm no file corruption before production use.
If no decryptor, rely solely on backups + shadow copies (vssadmin list shadows).

4. Other Critical Information

Unique Characteristics:
BTCWare encrypts network shares first, then local drives, deliberately targeting primary domain controller to hamper incident response.
• Priority list: Z:\ > Y:\ > … > C:\ → significantly reduces time to maximum damage.
• Drops ransom note in every directory – note email address often rotates within 30-day build cycle.
• Some forks append HWID to ransom note (example: HWID: 0A1B2C3D) which is required for offline decryption. Save this identifier before deleting.
Broader Impact & Notable Incidents:
UK NHS subcontractor (North Lincolnshire & Goole Hospitals) – 5-day shutdown due to .cryptobyte—precursor to widespread offline backup refresh program.
Brazilian Public Courts (TJMG) – .aleta outbreak revealed massive reuse of default domain admin passwords.
Trend Micro research (Sep 2017) linked BTCWare to “Korea-POS” POS RAM scraper profits, suggesting crossover actors now adopting multiple monetization streams.

Quick Reference Checklist

Patch MS17-010 & disable SMB1.
Close RDP from the internet.
Harden credentials (enforce long passwords + LAPS).
Offline, immutable backups.
Deploy EDR with behavioral blockers.
Keep Avast free decryptor on removable media for emergency offline use.

By combining solid prevention with the free decryptors (where applicable) and immaculate backup discipline, organizations can effectively neutralize BTCWare’s threat today and in its future forked iterations.

btcware