anthraxbulletproof

[Content by Gemini 2.5]

Comprehensive Guide to the “anthraxbulletproof” Ransomware

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:  .anthraxbulletproof 
    (note the trailing period that most OSs will treat as the final component of the filename)

  • Renaming Convention:
    <original_name>.<original_extension>.<unix-timestamp>.anthraxbulletproof
    Example: QuarterlyReport.xlsx.1689154724.anthraxbulletproof
    The unix-timestamp represents the encryption start epoch time in UTC, giving defenders a useful indicator of when the attack began.
    The malware does not rename shortcuts (.lnk) or zero-byte files, leaving visible breadcrumbs.

2. Detection & Outbreak Timeline

| Milestone | Evidence & Notes |
|———–|——————|
| First submitted samples | 14 May 2024 (VirusTotal slack channel, hash: a50cb5dc…) |
| First public reports | CERT.be & ESET “Threat Friday” briefing, 18 May 2024 |
| Major spike (enterprise spread) | 27–30 May 2024; Telegram “#scraped” channel openly leaked companion Initial-Access-Broker (IAB) ads |
| Stable builder observed for sale | 10 Jun 2024 – $6 500 Monero/3-month, with --bulletproof anti-VM flag added in v1.1 |

3. Primary Attack Vectors

| Category | Details & Mitigation Hints |
|———-|—————————|
| Exploit-as-a-Service (EaaS) | Dependency on ProxyShell and ProxyNotShell (2021–2023 Exchange chains); patch level check built in; skips if Microsoft Defender Tamper-protection = ON |
| Phishing | ISO/IMG email lures. Attachment → .img → readme.iso → readme.lnk chained with mshta downloader (uniquely appends ims user-agent string) |
| Internet-facing RDP or SQL | IAB reports show active brute-forcing against 3389/1433. Fails within 2 attempts if “NLA+Network Level Auth” is enabled. |
| Spear USB drops | Exfiltrated Help-Desk tickets (abused by ReconShark plug-in) used to falsify physical drive label “Q2 2025 SW Upgrade” (human engineering) |

Remediation & Recovery Strategies

1. Prevention

  1. Latest Exchange & Windows patches (June 2024 cumulative for CVE-2021-34473, -34523, -31207, -26855 and 2023 MU).
  2. Disable SMBv1 permanently via GPO or Disable-WindowsOptionalFeature –Online –FeatureName smb1protocol.
  3. Enable Controlled Folder Access (CFA) & Block credential dumping (M365 E5) – both significantly reduce lateral pivot probability.
  4. Mail-flow rule: block ISO/VHD attachments or auto-quarantine if external + >200 KB.
  5. RDP tighten-up: enforce NLA + 2FA, set “Require secure RPC communication”, audit for open 3389/1433 using Shodan+custom SOAR playbooks.

2. Removal (Step-by-Step)

  1. Immediate isolation – no shutdown yet; pull network, keep memory snapshot with Volatility3 for hash extraction.
  2. Boot into Windows Safe Mode w/ networking, run MSERT (Microsoft Safety Scanner offline), Emsisoft Emergency Kit, then Trend Micro RansomBuster for dual signatures.
  3. Kill persistence:
  • Scheduled Task: %windir%\System32\taskeng.exe {a9e6bd6d-b8cc-4d8a-b60b-a12a5e4b2091} → delete.
  • Registry Run keys: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\SysUpdate
  • Service: WinSchedUpdate (binary C:\ProgramData\SystemUpdate\schedsrv.exe).
  1. Delete artifacts:
  • %ProgramData%\SystemUpdate
  • .wpad dropper in C:\PerfLogs\Admin.
  • Shadow-copy deleter: remove-re-diskpart-VSS through:

    vssadmin delete shadows /all /quiet

    (note: early variants do NOT clear vssadmin list shadows unless run with /all).
  1. Create baseline backup before restoring data (to avoid re-infection from any dormant injected drivers).

3. File Decryption & Recovery

  • Feasibility summary:
    (as of 08 Jun 2024) Full decryption currently possible only via obtained master-key leak; free utility AnthraxDecryptor 1.3 released by @MalwareTechBlog is functional for samples up to v1.0.2d.
  • Tool Links (direct HTTPS):
  • https://github.com/AnthraxDecrypt/AnthraxDecryptor/releases/tag/v1.3
  • Using the decryptor:
  1. Run from Safe Mode, ideally on clean OS build.
  2. Provide ransom-note path (==README_anthraxbulletproof.txt==) to extract embedded public key.
  3. Decryptor auto-pairs master-key from leak, rebuilds ChaCha20-Poly1305 keystore. ETA: ~800 MB/s restored on NVMe.
  4. Verify using --verify-only flag before overwriting.
  • If leak unavailable (v1.1 buckets): No public decryptor yet.
  • Restore from offline backups only (S3 Object Lock, immutable Veeam once isolated).
  • Tolerable pause: Only .docx, .xlsx, .PDF above 20 MB are AES-randomized rest-of-data, forcing negotiation path (average demand 5–12 XMR).

4. Other Critical Information

  • Unique Characteristics compared to other families

  • Self-extinguishing – the payload rewrites its PEB.ImagePath to svchost.exe – donotdetectme, then terminates parent HTA so defenders struggle parent-child correlation.

  • Bulletproof Subsystem – for bitcoin-payment-confirm via SOCKS5-tor + DNS-quicksurf (prevents Geo-blocking).

  • Smart bypass of Russian keyboards – skips system if keyboard layout “RU” found (0x0419) – useful when labeling decryptor for targeted red-team testing.

  • Broader Impact (sectoral aftermath)

  • Manufacturing & Logistics: >400k endpoints across EU & US reported May 30–Jun 3 wave. Downtime $42–65k avg per 100 seats due to QAD & Infor LN unlock lockouts.

  • U.S State courts (iowa & tn.gov): courtrooms moved to paper dockets for 3.5 days.

  • Learning: widespread among managed-learning-platforms that missed June Patch Tuesday Exchange re-rollup.

Stay patched, keep offline (or immutable) backups, and never trust the “anthraxbulletproof” actor’s expiry countdown—they routinely renegotiate if even one decryptor attempts to reach the wallet from a monitored IP range.