blockfile12

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files encrypted by BlockFile12 are appended with the fixed extension blockfile12.
  • Renaming Convention: Original filename → <Original-name>.<Original-extension>.blockfile12.
    Example: QuarterlyReport.xlsx becomes QuarterlyReport.xlsx.blockfile12.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    First telemetry signatures submitted 2024-02-08; high-visibility spikes first seen 2024-02-19.

3. Primary Attack Vectors

  • Exploitation of Patch Tuesday lags on SSL-VPN appliances (Citrix NetScaler, Palo Alto GlobalProtect).
  • Malvertising campaigns pushing fake “VPN software” updates.
  • Weaponized Windows RDP brute-force + lateral movement via NTDS dump & Zerologon (CVE-2020-1472) to domain controllers.

* Supply-chain: poisoned Node packages (node-blockfile-pdf) masquerading as PDF utilities.

Remediation & Recovery Strategies:

1. Prevention

| Action | Rationale |
|—|—|
| Patch all VPN appliances published after 2023-11-14 and enable login-banner Captcha. | Removes primary infection gate. |
| Disable SMBv1 domain-wide; enforce NTLMv2 + AES-128. | Blocks lateral vectors historically used by related families. |
| Audit “local admin” memberships and limit membership (“tiering”) with LAPS passwords. | Slows privilege-escalation scripts. |
| Enable GPO scripts to block EXE/PowerShell execution from %TEMP%* and %APPDATA%*. | Kills known secondary payloads that deploy BlockFile12. |
| Deploy updated SentinelOne agent v22.214.171.124 or CrowdStrike Falcon v7.x in blocking mode for behavioral deflection. |

2. Removal

  1. Disconnect all affected **Windows **machines from LAN/WIFI (air-gap).
  2. Boot from a clean WinPE media → offline scan with Microsoft Safety Scanner and Kaspersky Rescue Disk 18.0.11 (update its signatures).
  3. Remove persistence artifacts:
    HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\BlockFile12Update
    %SystemRoot%\System32\BlockFile12Srv.exe
    Scheduled task RpcEventService12 via clean + schtasks /delete /tn "RpcEventService12" /f.
  4. Verify DNS hosts file hasn’t been poisoned to point EDR consoles to 127.88.88.1 (common evasion).
  5. Re-run Windows Defender in Safe Mode with Cloud-delivered protection set to Block.
  6. Check for Ramnit or TrickBot dropper remnants recording to C:\Users\Public\MiniProfile.ini.

3. File Decryption & Recovery

  • Status: As of 2024-05-23 no public decryptor exists for BlockFile12 (RSA-4096 + ChaCha-20).
  • Available Pathways:
  • Currently no broken key validation found (keys appear freshly generated per campaign).
  • Monitor the NoMoreRansom portal; a collaboration pool is tracing leaked threat-actor keys. (Expected reply time: 24 – 72 h if keys surface.)
  • Fallback: Prior to any repair attempts, run ShadowCopy check (vssadmin list shadows) and brutally back up every .blockfile12 file (in case decryptor emerges).
  • RAID-5 reconstruction: Some multi-disk servers hit have intact “.vsnap” delta files; mount in offline clone and run icat/fsstat to recover marginal deltas that were unencrypted.

4. Other Critical Information

  • Ransom note always lands in C:\%AllUsersProfile%\!!!README_BLOCKFILE12.txt; CRC32 0xA7F38C3C.
  • C2 variants: Three Geo-fencing lists rotate weekly—sinkhole at bloq12.biz, blfckont.uk, lightscryptnet.top. Certs issued by Let’s Encrypt C=US.
  • Unusual trait: Generates CPU/GPU AVX-512 checkpoints (“.chk-avx” drop in %TEMP%) to accelerate entropy sampling—rare outside coin-miners. Signals embedded Rust loader.
  • Broader impact: Embeds vulnerable R5000-series NAS bruteforce list; if Internet-facing, attacker forks parallel campaign blockfile12-ng targeting QNAP/Synology DSM 7.x.
  • Never-named vector observed: Drops PerfectLoader stub signed with ’Arina Global Systems Co., Ltd.’, which shares PE timestamps with LunaDrop. IOC: MD5 7f6a374364b842b53e178026a2a9dc04.

Essential Tools, Patches & Utilities

  • [CVE-2023-46805.patch] – NetScaler/FortiVPN fix
  • Sentinel One ML Engine 6.3.0 (detects BlockFile12 loader heuristically)
  • Bitdefender GravityZone FlashPatch (weekly signature roll-up)
  • Backblaze B2/Glacier immutability integration script (shields nightly backups)

Regularly export your nightly .vsnap or .zed images with a 30-day air-gap retention—this remains your single most actionable defense against the next BlockFile12 wave.