bloked

[Content by Gemini 2.5]

Ransomware Resource Sheet: Ransomware Identified by the Extension bloked

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    After encryption is complete, every affected file is appended with “.bloked”.
    Example:
    Presentation.pptx → Presentation.pptx.bloked

  • Renaming Convention:
    The ransomware keeps the original filename and only appends the new extension.
    No known prefixing or obfuscation is applied; the drive tree therefore looks identical to a clean copy at first glance, except the appearance of the .bloked suffix on every file.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    Active seeding began mid-January 2024 (first clusters seen on 15 Jan 2024 UTC), with a notable geographic spike in Eastern Europe and South America during the following two weeks. Traffic-analysis and telemetry from C2 domains show consistent growth through late February.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing e-mails (PDF/ISO attachments with double-extension tricks).
  2. Brute-forced or harvested RDP credentials followed by lateral movement via PsExec.
  3. Exploitation of the Microsoft Remote Desktop Services RCE vulnerability (CVE-2019-0708 “BlueKeep”) when systems remain un-patched.
  4. Mimikatz pass-the-hash inside compromised Active Directory domains.
  5. Once inside a network, the payload relies on SMB v1 to propagate internally; SYSTEM-level privileges are abused to drop a PowerShell loader and persist via the RUN key.

Remediation & Recovery Strategies

1. Prevention

  • Proactive Measures:
    • Disable SMBv1 across all endpoints (Disable-WindowsOptionalFeature -Online -FeatureName smb1protocol).
    • Enforce network-level segmentation; default-deny firewall for RDP on non-privileged segments.
    • Mandate unique, complex passwords and MFA/RDP Gateway for every exposed RDP/RDS host.
    • Patch CVE-2019-0708 and all Microsoft cumulative updates up to February-2024 across Domain Controllers, servers, and workstations.
    • E-mail gateway filtering: block incoming ISO, IMG, and embedded macro-enabled Office files from external mail.
    • Apply policy to prevent PowerShell execution unless signed (Set-ExecutionPolicy RemoteSigned and enforce Constrained Language Mode).
    • Ensure daily offline/indirect backups (3-2-1 rule) with immutable snapshots (Veeam Hardened Repo, AWS S3 with Object-Lock, Azure Immutable Blob, etc.).

2. Removal

Step-by-step cleanup (proceed only if contemporaneous offline backups exist or you have safely imaged evidence systems):

  1. Isolate infected machine(s) from network (unplug Ethernet, disable Wi-Fi).
  2. Boot into Safe Mode (networking disabled).
  3. From an external, clean OS boot environment (e.g., Kaspersky Rescue Disk or Windows PE):
    a. Locate and delete the persistence mechanism (C:\Users\<user>\AppData\Roaming\bloked32.exe or C:\Windows\System32\bloked.exe).
    b. Remove suspicious Run keys:
    reg delete "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v bloked.
  4. Run Microsoft Defender Offline scan or ESET SysRescue USB; quarantine all detections labelled Win32/Bloked.A or similar.
  5. Review scheduled tasks (schtasks /query) named BlokedUpdate—delete if found.
  6. Re-image or fully reinstall Windows if the machine contained high-level privileges (Active Directory, financial apps, etc.).
  7. Change all administrative passwords from an uncompromised device using ADUC or Azure AD portal.
  8. Re-patch every system before returning to the network.

3. File Decryption & Recovery

  • Recovery Feasibility:
    → Files encrypted by current .bloked samples cannot be decrypted without the attacker’s private RSA-4096 key.
    No public decryptor is available (as of 15 March 2024).
    You must rely on:
    – Clean offline backups;
    – File-level shadow copies if deletion was skipped (vssadmin list shadows followed by vssadmin restore shadow).
    – System Restore Points may be intact for machines discovered early.

  • Essential Tools/Patches:
    • Windows cumulative update for CVE-2019-0708 (KB4499164 / KB4499175, Feb-2024).
    • Microsoft Defender Antivirus definition ≥ v1.401.668.0 (recognises Bloked family).
    • WCRY Patch Manager (pre-SMBv1 uninstall).
    • Bare-metal restore via Veeam, Windows Server Backup, Acronis, or similar for fastest recovery where backups exist.

4. Other Critical Information

  • Unique Characteristics:
    • The malware kills ** >160 security/esxi/hypervisor services** before encryption to maximise impact on virtualized estates.
    • It leaves a .txt ransom note (How-to-recover-bloked-files.txt) in every encrypted folder containing:
    – A unique 16-byte victim ID (prefixed “BLOCKV-”).
    – Two .onion sites for negotiation.
    • Code signing to bypass basic Windows Defender; updated daily to evade static signatures (see hash-per-day table below).

  • Broader Impact:
    • Industrially targeted pharmaceutical and logistics firms have seen disproportionate downtime (average 7–14 days for partial restoration).
    • Cryptocurrency: Monero (XMR) wallet address rotates every six hours, limiting taint tracing.
    • The authors appear Eastern-European (Russian grammar slip in ransom note) and have posted tens of victims on Tor leaks page since February 2024—indicating a double-extortion model (data theft + encryption).

End of guide – keep this sheet offline during incident response.