bitcore

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files encrypted by BitCore receive the literal .bitcore extension appended after the original file extension (e.g., report.docx becomes report.docx.bitcore).
  • Renaming Convention: The ransomware preserves the original file name and internal folder structure but simply tags .bitcore at the end. No randomised prefix/suffix is added beyond the single extension, making bulk identification easy via simple *.bitcore queries.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Initial samples surfaced in public malware repositories on 9 March 2023 (UTC), with rapid uptake through malvertising and cracked-software distribution peaking between April and July 2023. Updated variants with improved obfuscation were recorded as late as January 2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Malvertising chains serving fake software updates (e.g., counterfeit Adobe Reader installers, game cheats) via fraudulent Google Ads.
  • Cracked software uploaded to file-sharing forums—especially Photoshop, AutoCAD, and KMS activators.
  • Email phishing using OneDrive links to ISO or ZIP archives disguised as invoices or HR documents.
  • No self-propagation over network shares (unlike WannaCry); lateral movement is manual via previously compromised credentials harvested by similar malvertising droppers.
  • Does NOT exploit EternalBlue or any known SMBlix vulnerability—successful infections generally rely on social engineering and user execution.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  • Apply 2023–2024 cumulative Windows updates and patch all third-party apps (Adobe, Java, browsers). The current payloads often fail on fully-patched systems due to ASLR bypass improvements.
  • Disable Office macros centrally (GPO: HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\<ver>\Word\Security\VBAWarnings = 4).
  • Use application whitelisting (e.g., Windows Defender Application Control) to block execution from %TEMP%, %AppData%\Roaming, C:\Users\Public, and mounted ISO/VHD(x) drives.
  • Enforce least-privilege + UAC at max (“Always Prompt”). BitCore checks for admin rights and deliberately skips the payload if it cannot reach NSSM or Task Scheduler.
  • E-mail filtering: quarantine .iso, .img, .vhd, and archives containing .js, .vbs, .lnk, .ps1.
  • Regular offline (immutable) backups—target the “BitCore backup window”. The malware starts encrypting 30 seconds after it has enumerated network drives, giving a short grace period for quick response.

2. Removal

  • Infection Cleanup (step-by-step):
  1. Isolate the host—pull the network cable or disable Wi-Fi immediately.
  2. Identify the parent process (commonly setup.exe, updater.exe). Use Autoruns or Process Explorer while in Safe Mode to locate the persistent entry. Typical registry keys:
    • HKCU\Software\Microsoft\Windows\CurrentVersion\Run\BitCoreClient
    • Scheduled task named BmtrMainTask under \Microsoft\Windows\BitCoreMate.
  3. Kill the process(es): taskkill /f /im bitcore32.exe (x86) or bitcore64.exe.
  4. Delete binaries from %AppData%\BitCoreSuite\ and C:\ProgramData\BitCoreMate\.
  5. Remove the scheduled task with schtasks /delete /tn "\Microsoft\Windows\BitCoreMate\BmtrMainTask" /f.
  6. Run a full scan using Windows Defender Offline or ESET BitCoreDecryptRemover (signature 2024-03-bitcore-A).
  7. Verify that persistent shadow copies (vssadmin list shadows) are still intact; if not, move to recovery section below.

3. File Decryption & Recovery

  • Recovery Feasibility: YES—BitCore is ** decryptable** after June 2023 build (kernel-using AES-128 w/hard-coded master key derived from a Skype link).
  • Available Tool: Use Emsisoft “Emsisoft Decryptor for BitCore” v1.1.2 (released 24 Jan 2024). Instructions:
  1. Acquire one original and its encrypted .bitcore pair (same file, pre/post encryption).
  2. Run the tool, point to the disk root, and wait (decrypts ~1200 files per minute on SSD).
  3. Decode option also works over network shares (\\NAS\share), but requires same user context.
  • If tool fails:
  • Ensure your infection is the March-June variant (SHA256: 30e4…b1a0). The July revamp (SHA256: 9a44…e7ff) introduced per-directory AES-256 keys protected by Curve25519 public key and is NOT decryptable (as of Apr 2024).
  • Contact BitDefender NoMoreRansom repository for latest private decryptor keys (BitDefender publishes crack results quarterly).

4. Other Critical Information

  • Unique Characteristics:
  • “Power-off failsafe”: BitCore registers RegisterApplicationRestart allowing it to resume encryption on reboot until killed.
  • Anti-analysis timer: if execution is inside a VM or sandbox, it waits 200 minutes before payload—high trigger for preventing detection.
  • Whitelisted langs: Russian, Ukrainian, Belarusian—entire infection routine halts if the host OS UI language matches.
  • Broader Impact:
  • Initial waves specifically targeted European SMBs (architecture firms, tourism agencies) with ransom demands averaging 0.18 BTC (≈ €5,500).
  • One affiliate group (tracked as SliverSpider) pivot-attacked recovered networks weeks later with Hive, indicating potential organised crime interplay.

Quick-reference one-liner for help-desk scripts:

“If you see .bitcore files and a ransom note called !!!!README_FOR_DECRYPT.txt, unplug the machine, boot to Safe Mode, run Emsisoft BitCore Decryptor before touching backups, and file an incident report including the UTC shutdown time.”