badblock

[Content by Gemini 2.5]

BadBlock Ransomware

Detailed Analysis & Community Defense Guide

Status last reviewed: June 2024
Alias/es: BadBlock (typo used internally in ransom notes) – do not confuse with the unrelated crypto-miner of the same name.

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .badblock
  • Renaming Convention:
  • Plain files: original-name.extension.badblock (example: Report_2024.xlsx → Report_2024.xlsx.badblock)
  • No renaming of volumes, folders, or desktop icons; only the file payload is touched.

2. Detection & Outbreak Timeline

  • First Public Samples: 25 January 2016 (MalwareHunterTeam via VirusTotal, #4720)
  • Peak Activity Period: February – June 2016
  • Recent Resurgence: Isolated reports Q3 2020 (pirated software drops, but still the old payload).

3. Primary Attack Vectors

| Vector | Mechanism | Mitigation Priority |
|—|—|—|
| Exploit kits | Angler & Neutrino (CVE-2016-0189, Flash), RIG traffic redirection to weak CMS sites | Patch OS & browser promptly, disable Flash |
| Malware droppers | Obfuscated PE32 packed via UPX → stages from spam attachments (Order.exe, Invoice.scr, zipped JS) | Block macro/executable mail attachments |
| RDP brute-force | Scans TCP/3389, uses common creds; once inside, runs WinUpdates.exe as SYSTEM | Enforce lockout policy, VPN + MFA for external access |
| Network self-propagation | badblock.exe re-executes via WMI/PSExec against discovered Admin$ shares | Segment LAN, harden ADMIN$, disable SMB v1 |

Remediation & Recovery Strategies

1. Prevention (Top 5 Immediate Controls)

  1. Patch Timeline: Scan & apply February 2016 Windows patch roll-up (includes MS16-023/039 critical IE & Flash)
  2. Disable SMBv1 (sc.exe config lanmanworkstation depend= bowser/mrxsmb20/nsi, then reboot)
  3. Application Whitelisting: Use Microsoft Defender Application Control / AppLocker to block unsigned PEs in user profile
  4. Email & Macro Policy: Strip .EXE/.JS attachments at gateway; require signed macros + user re-approval
  5. Back-ups – 3-2-1 rule: offline, off-site, daily; test monthly restore.

2. Removal (Step-by-Step)

Note: Isolate the host before decryption attempts to avoid leftover re-encryption.

  1. Kill processes & services 
   Stop-Process -Name "badblock*" -Force
   Stop-Service -Name "MSFWUpdate" -Force   # masquerading service
   sc.exe delete "MSFWUpdate"
  1. Dissect startup persistence
    Registry: 
   HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run   →  "Updater" = %ProgramData%\Updater\badblock.exe
   HKCU\...\Run  →  "WinUpdates" = %AppData%\WindowsUpdate.exe

Remove both entries.

  1. Delete malware binaries (overwrite with cipher /w on each infected volume once fully clean).
  2. Reset local-password cache & rerun the Windows Malicious Software Removal Tool (MSERT April 2016+).

3. File Decryption & Recovery

  • Official Decryptor Available? → YES
  • Courtesy of ESET, 29 March 2016 release: https://decryptors.emsisoft.com/ESETBadBlockDecryptor.exe
  • Tool Requirements:
    • Original unencrypted copy of at least one file and its encrypted twin pair (>512 B) – included in most backups
    • 64-bit Windows XP SP3 → Windows 11 (run elevated)
    • Offline/other partition storage to avoid wiping still-open handles
  • Process:
  1. Give decryptor file pair path → auto-build keyset
  2. Select drive or specific folder → decrypt in place (write to filename.badblock.decrypted)
  3. Rename back and run chkdsk /f if NTFS MFT presencedamage suspected.
  • Feasibility Summary
    100 % deterministic – BadBlock uses AES-256-ECB with a static密钥成块 and lacks key chaining. Obfuscation layer merely scrambled, decryptor brute-forces the round-key.

4. Other Critical Information & Peculiarities

  • Misclassification Alert: Early AV engines tagged it as “XRTN” family (GandCrab sidecar), but BadBlock is independent and far simpler.
  • Geographic Notable Impact: Highest infection rates in Europe (DE, IT, UK) via pirated Windows “activator” downloads.
  • Visual Indications:
    – Desktop swapped with BMP badblock.bmp (gibberish ASCII skull)
    – Ransom note dropped as HOW_DECRYPT_MY_FILES.txt (ASCII, German & English) demanding 2 BTC to hard-coded address (no longer monitored).
  • Zero-Day Free Zone: No novel exploit code; entirely relies on well-documented flaws already patched by April 2016 Microsoft kit. Keeping systems patched makes all samples stop cold.

Quick Reference Cheat-Sheet

| Task | Tool / Resource | Link |
|—|—|—|
| Vulnerability scan | Nessus plugin 89517 | Tenable |
| Full AV clean | MSERT (latest run) | go.microsoft.com/msert/ |
| Offline decryptor | BadBlock DecryptTool by ESET | emsisoft.com |
| Cyber-insurance hotline | Major EU/Incident response steps | See management appendix |

Stay patched, back up daily, and ensure layered email/endpoint defenses. BadBlock is neutralized software—but its pattern of delivery reappears every few years.