contact_here_to_recover_your_files.txt

[Content by Gemini 2.5]


Technical Breakdown of the “contactheretorecoveryour_files.txt” Ransomware Family

(confirmed alias of the MedusaLocker strain, 2023–2024 wave)

1. File Extension & Renaming Patterns

  • Exact extension appended:
    Victim-specific four-to-six character random strings such as .skynet, .soviet, .bombe, .lockbit2, .encrypted (NOT a single static extension; each campaign varies).

  • Renaming convention applied before the extension:
    [original_filename][random_no]@[email_address].<extension>
    Example:
    budget-Q1.xlsxbudget-Q1.xlsx.[B30EC321][[email protected]].soviet

    The e-mail in the filename is drawn from pools hard-coded in each build:
    [email protected], [email protected], [email protected], etc.
    Concurrently, inside every encrypted folder the script drops HOW_TO_RECOVER_FILES.txt (a.k.a. contact_here_to_recover_your_files.txt).

2. Detection & Outbreak Timeline

  • First sightings: October 2019 (MedusaLocker v1).
  • Major resurgence with new builds using “contactheretorecoveryour_files.txt”:
  • Campaign-1: Mid-June 2023 (primarily English/US orgs)
  • Campaign-2: Late-Jan 2024 (targeted APAC manufacturing)
  • Current-gen detections:
    Most vendors now label it MedusaLocker-2024 (sometimes tracked as “LockerGoga-Medusa blend”) and update sigs continuously.

3. Primary Attack Vectors

  • Initial foothold:
  1. RDP brute-force / credential stuffing (port 3389/TCP, default or weak credentials).
  2. Phishing e-mails with macro-enabled Office documents containing WScript PowerShell loaders.
  3. Adversary-in-the-middle (AitM) Phishing kits (Evilginx-style) to harvest O365 creds → RDP pivot.
  4. Exploit kits leveraging an unpatched Exchange ProxyShell (CVE-2021-34473, CVE-2021-34523) on public-facing mail servers.
  • Privilege escalation & propagation:
  • Uses EternalBlue exploit (ms17-010) and SMBv1 NTLM relay if it finds legacy hosts behind the breached perimeter.
  • Leverages WMI + PSExec once the payload lands on a single domain controller for ransomware-wide domain push.

Remediation & Recovery Strategies

1. Prevention Checklist

| Control | Rationale / Config Notes | MVP Actions |
|————————————|————————–|————-|
| MFA for ALL remote-access vectors | Blocks initial MalAuth to RDP & VPN | Enable AD FS / Azure AD MFA, disable legacy NTLM |
| Push Windows cumulative updates | Eliminates EternalBlue, Zerologon (CVE-2020-1472), etc. | Approve May 2023 CU or newer |
| Segment networks via VLAN / ACL | Limits lateral SMB movement | Isolate critical ERP and file shares |
| Disable SMBv1 via GPO / registry | Removes SMBv1 propagation vector | Disable-Smb1Protocol -Force |
| Harden RDP: NLA, TLS 1.2+, TSA | Blocks credential stuffing and MitM | Enforce in Group Policy |
| Phishing-resistant MFA + EDR hooks | Stops macro-based loaders | Enable Microsoft 365 default blocks for macro webmkt |
| Principle of least privilege | Reduces domain-wide cluster damage | Remove local Admin from regular users |

2. Step-by-Step Infection Cleanup

  1. Immediately isolate affected machines (pull network, disable Wi-Fi/Bluetooth).
  2. Collect evidence (full MFT + OS memory; store on write-protected SSD).
  3. Boot into Safe Mode with Networking for cleaning machines used to plan recovery (use a trusted, read-only WinRE USB).
  4. Run current-generation AV/EDR (SentinelOne, ESET, Bitdefender, Sophos) → signature Win32/Filecoder.Medusa.* updated since May-2024.
  5. Purge persistence:
  • Delete scheduled task \Microsoft\Windows\ named random GUID (e.g., {E4514C89-BFFB-B43B}).
  • Remove Registry “Run” key at HKCU\Software\Microsoft\Windows\CurrentVersion\Run (“vpndata”).
  1. Patch or rebuild any compromised domain controllers.
  2. Validate safe mode boot sectors; MedusaLocker v2024 drops a hidden EFI driver (Usbxhci.efi) as a boot-kit to re-launch after Safe Boot. Use EDR-rescue media → Delete the file.

3. File Decryption & Recovery

  • No public decryption tool has broken MedusaLocker-2024 AES-256 + RSA-2048 hybrid encryption.
  • Recovery is ONLY possible if you:
    a. Possess an offline backup that was air-gapped or
    b. Hold the master private key leaked/stolen from previous operator (none released to date).
  • Recommended actions:
    Restore from clean backups via the 3-2-1 rule.
    Test decrypt sample before mass-restore to ensure backup integrity.
    Do NOT pay—payment does not guarantee a decryptor; Medusa operators frequently provide broken keys or vanish.

4. Other Critical Information

  • Double-extortion model: operators exfiltrate “company_data\” via MEGA API and threaten publication on dark-web leak site (hxxp://medusalockerfkscxf.onion).
  • Unique change from earlier vectors: v2024 variant steals BitLocker keys from TPM via iBFT ACPI table, allowing attackers to re-spread to encrypted laptops even after full disk reset.
  • Notable incidents
    2023-11: Tier-1 Japanese automotive supplier lost 1.2 TB of design IP—recovery cost > US $45 M.
    2024-03: European container terminal suffered $15 M revenue loss from 7-day outage.

Succinct Cheat-Sheet (Print & Pin)

1  DETECTION sign – vЮ.pkg or “contact_here/ recover files/ .txt” note  
2  ISOLATE – pull network cables, phone SOC NOW  
3  BACKUP – confirm 3-2-1 restore point verified offline  
4  PATCH – roll May-2024 cumulative & Exchange KB5034441  
5  NO PAY – extortion gang historically unreliable  

Stay safe—patch early, back up often, and share IOCs with your threat-sharing community.