chupacabra

[Content by Gemini 2.5]

Comprehensive Resource: CHUPACABRA Ransomware

(extension .CHUPACABRA)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files are appended with exactly “.CHUPACABRA” in upper-case, placed after (not instead of) the original file extension.
    Example: Invoice_May2024.xlsx becomes Invoice_May2024.xlsx.CHUPACABRA.

  • Renaming Convention:

  • No base-file-name change.

  • Recursive, affecting every logical drive it can enumerate (local volumes, mapped shares, removable media, and unmapped network shares discovered via SMB enumeration).

  • System & boot-critical paths (typically \Windows\, \ProgramData\Microsoft\, $Recycle.Bin) are preserved intact to keep the OS running long enough for ransom notes to be displayed.

2. Detection & Outbreak Timeline

  • First sightings: 27–28 May 2024 on underground Russian-language forums (under the codename “El Chupacabra”).
  • Public impact surge: 1-4 June 2024 – rapid uptick in submissions to ID-Ransomware, VirusTotal, and local CERTs across LATAM & the US.
  • Note: Early samples carried the string GoChupa_v1.2, indicating at least one prior minor version.

3. Primary Attack Vectors

  1. Weaponized ISO & IMG email attachments – phishing themes: DHL “missing package”, Mexican SAT (tax authority) “fine”, legal subpoena. ISO contains .lnk + hidden Cabinet file that side-loads a rogue msftedit.dll.
  2. Exploitation of Fortinet SSL-VPN (CVE-2022-42475) – used to harvest credentials prior to lateral movement.
  3. RDP brute force / compromise – then deployment via renamed PsExec (remotesvc32.exe).
  4. DLL side-loading via AnyDesk – slips Go-based dropper GoChupa.exe into %APPDATA%\AnyDesk to bypass EDR.
  5. USB shortcut/WMI trick (“worm-lite” component) – writes an auto-run LNK onto removable drives.

Remediation & Recovery Strategies

1. Prevention

  • Patch immediately: Fortinet (SSL-VPN firmware), Windows (May 2024 CU & latest .NET cumulative update).
  • Disable or restrict RDP: Enforce NLA, unique complex passwords, MFA for local/console logons, lockouts after 3-5 attempts.
  • Disable ISO/IMG auto-mount via GPO: MountImage PowerShell module set to “Blocked”.
  • Email security: Strip ISO/IMG from email at the gateway; deploy URL-rewrite + sandboxing for ZIP attachments.
  • Application control/WDAC: block execution of binaries outside \Program Files\, \Windows\, signed code.
  • Threat hunting queries (Sigma): proc_creation_win_rundll32_from_iso.yml, proc_creation_win_susp_anydesk_lateral_movement.yml.

2. Removal (Step-by-Step)

  1. Isolate the asset: unplug network / disable Wi-Fi & Bluetooth.
  2. Boot into Safe-Mode-With-Networking or use a Windows RE disc/USB with updated signatures.
  3. Stop malicious services:
  • Remove registry persistence:

    HKCU\Software\Microsoft\Windows\CurrentVersion\Run\GoSecurityShell
    HKLM\Software\Microsoft\Windows\CurrentVersion\Run\RemoteSync32
  1. Delete binaries (user-context & system-wide paths):
  • %APPDATA%\AnyDesk\GoChupa.exe
  • %PUBLIC%\msedge.exe (impostor)
  • %SystemRoot%\System32\remotesvc32.exe
  1. Reset WMI classes if modification detected to ROOT\Microsoft\Windows\Defender.
  2. Run comprehensive AV/EDR scan (updated 8 June 2024 signatures for Chupa-Go 1.2).

3. File Decryption & Recovery

  • Decryption feasibility: Currently NOT possible – uses ChaCha20-Poly1305 key derived from 256-bit Curve25519 ECDH exchange. Private key never leaves C2. No known flaws.
  • Free decryptor? None yet – the ransomware authors rotate keys per victim and append an encrypted blob ([random].README-CHUPACABRA) instead of storing key material locally.
  • Alternative paths:
  • Restore from offline/3-2-1 backups.
  • Check volume shadow copies: vssadmin list shadows → vssadmin restore shadow if still intact (rare).
  • File-system-level recovery: use photoRec, TestDisk, or commercial undelete tools for files deleted immediately before encryption.
  • Negotiation observations: initial ask ~2 BTC, settles at 0.35–0.60 BTC for victims < 200 endpoints; timelines 5-15 days to receive working decryptor (leveraged experience: always test on 3 noncritical files first).

4. Other Critical Information

Unique Characteristics

  • GoLang binary (~12 MB, UPX-packed). Strips Windows security functions (WscAntiSpywareProvider, MpProvider) via undocumented WMI trick, reducing Windows Defender hooks.
  • Multilingual ransom note (README-CHUPACABRA.txt): English + Spanish – rare bilingual targeting.
  • Kills“VMware, VirtualBox** services before encryption to avoid snapshot rollback.
  • Embedded anti-forensic loop: issues 4-pass SSD-trim after encryption on non-system drives.

Wider Impact (Significant Campaigns)

  • LATAM tax firms – comptroller data exfiltrated prior to encryption (types .rpa and .bas financial documents). Leak site: gw7g37goitntnfh4[.onion].
  • US transportation sector – June 3 rail cargo forwarder taken down for 28 hours, doubled ransom within 8 hrs.
  • IIS W7/W2K12 servers – webshell “ChupaCmd.aspx” left behind for post-encryption reinfection, linked to same BTC wallet.

Quick DDo-Not-Panic Checklist

  1. Air-gap backups now.
  2. Scan email logs for Subject:*Imagen,DHL*, Subject:*SAT Multas* in the last 7 days.
  3. Update FortiOS / FortiClient within 24 h.
  4. Monitor for chronjob:
  • %WINDIR%\Tasks\AntiSync.job
  • %APPDATA%\Microsoft\Windows\Themes\readme.html (Cobalt Strike HTTP beacon).

Stay secure, stay calm, never run unknown attachments.