[email protected]

[Content by Gemini 2.5]

Ransomware Brief: The [email protected] Strain

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: All successfully encrypted files receive the appended [email protected] suffix (e.g., report.xlsx → [email protected])
  • Renaming Convention:
    – File name itself does not change; only the extension is added successively (double-extension).
    – No additional prefixes (no hex-coded initials or random 8-byte strings). Perfect example: [email protected].

2. Detection & Outbreak Timeline

  • First widely-discussed samples: mid-January 2023 via Ukrainian SOC bulletins.
  • Global spike: late February–March 2023 (geo-targeting shifted to Western Europe & North-America).
  • Active campaign status: Still under incremental updates through RaaS (Ransomware-as-a-Service) offerings on mid-tier criminal markets.

3. Primary Attack Vectors

| Vector | Typical Details |
|—————————————-|———————————————————————————————————–|
| Phishing e-mail with OneNote attachments | Malicious “.one” files containing embedded HTA/VBS scripts; lures resemble invoices or PayPal receipts. |
| RDP brute-force (TCP/3389) | Engines drop Cobalt Strike beacons then manual PSExec push of the ransomware payload (majLoader.exe). |
| ProxyShell chain (CVE-2021-34473) | Exploits still seen against unpatched Exchange 2013/2016/2019; shell-commands drop PowerShell stagers. |
| Smuggling via compromised web-sites | Fake browser-update pages pushing JavaScript bundles that spawn the ransomware once user clicks “Allow”. |

Remediation & Recovery Strategies

1. Prevention

| Step | Action | Command / Reference |
|——|——–|———————|
| Windows patch baselining | Install every Security-only or Monthly Rollup ≥ Aug-2021 to fully mitigate ProxyShell | wusa.exe Windows10.0-kb5005033-x64.msu |
| Disable SMBv1 & close irrelevant ports | Registry / group-policy disable + firewall rules for 135/139/445/3389 | Set-SmbServerConfiguration -EnableSMB1Protocol $false |
| Local credential hygiene | Enforce 14-char min, complexity, 14-day age rotation; ban password reuse. |
| Email gateway hardening | Strip one, onepkg, iso, disables VBA macros by default; quarantine HTA & VBS. |
| Application whitelisting & EDR | Enable Microsoft Defender ASR (Attack Surface Reduction) rules (Block executable content from email client and webmail). |
| Offline & isolated backups | 3-2-1 rule + immutability (WORM) for cloud snapshots (e.g., Azure Blob “immutable” tiers). |

2. Removal (Step-by-step)

  1. Physically isolate infected hosts (pull LAN/Wi-Fi cables; disable Wi-Fi/BT via BIOS when possible).
  2. Boot from offline Windows PE / WinRE USB (MS DaRT, Hiren’s PE, Kaspersky Rescue Disk).
  3. Delete persistence artifacts:
    – %AppData%\Microsoft\Windows\Start Menu\Programs\Startup\majStart.exe
    – Scheduled Task \majSync -> schtasks /Delete /TN "majSync" /F
  4. Quarantine registry keys:
    – HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\majServ
    – HKLM\SYSTEM\CurrentControlSet\Services\majDef
  5. Run vendor-remediation engine:
    – ESET Emergency Kit: ecls.exe /clean /delete /log=c:\quarantine\log.txt
    – Malwarebytes ADW offline build if WinPE supports it (/scan /clean).
  6. Re-image only if OS integrity check (sfc /scannow) returns collateral damage.

3. File Decryption & Recovery

  • Recovery Feasibility: No public decryptor for [email protected] as of 2024-05. Encryption uses a per-file ChaCha20 key wrapped with RSA-2048 OAEP.
  • Official private keys never released; no patent weakness identified.
  • Options left:
    – Locate shadow-copy snapshots (vssadmin list shadows) → if ransomware