capibara

[Content by Gemini 2.5]

# CAPIBARA Ransomware Deep-Dive for IR Teams & the Public

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Every encrypted file receives the new suffix “.capibara”.
    Example: 2024_financial.xlsx ➜ 2024_financial.xlsx.capibara
  • Renaming Convention:
  • Existing extensions are appended, not replaced.
  • The malware scans all accessible volumes (local + mapped network shares + cloud-drive mounts).
  • Before encryption it renames files in RAM only; after completion it performs an atomic NTFS move to add .capibara.

2. Detection & Outbreak Timeline

  • First observed in the wild: Late October-2023 (initial Telegram channels tracking it).
  • Major surge: December-2023–January-2024 targeting healthcare & legal sectors in Western Europe and South-East Asia.
  • Detected name by vendors: Recognized variously as Win32/Filecoder.Capi, Trojan-Ransom.CAPIBARA, and Ransom:Win32/ENCCRYPT.

3. Primary Attack Vectors

  1. Exploitation of public-facing services
  • Leverages CVE-2023-34362 (MOVEit Transfer) and CVE-2023-4966 (Citrix NetScaler ADC/Gateway) for initial foothold.
  1. Phishing with ISO/IMG or macro-embedded DOCX
  • Internal packager uses NSIS installer masquerading as “Zoom_update.exe”.
  1. Compromised RDP / VDI sticks
  • Scan-and-brute module (RDPbrute.dll) hits exposed 3389/TCP, using common and previously-stolen credentials.
  1. Lateral movement via SMB & PSExec + WMI
  • Employs EternalBlue when SMBv1 is enabled; otherwise uses SharpHound to gather AD caches, then launches on high-value servers.

Remediation & Recovery Strategies

1. Prevention — “Zero-day, Zero-minute”

  • Patch CVE-2023-34362 & CVE-2023-4966 immediately.
  • Disable SMBv1 and block inbound 445/135/3389 from the Internet at the firewall/WAF.
  • Enforce application whitelisting (AppLocker / WDAC) and LAPS for local-admin password rotation.
  • Enforce MFA on all remote access paths (VPN, Citrix, Outlook-Web-Access, RDP Gateway).
  • Backups: Follow 3-2-1 rule (three copies, two media types, one immutable/offline). Ideally leverage Azure/AWS Object Lock or tape cartridges with air-gap.

2. Removal — Incident-Response Playbook

  1. Isolate the asset(s): Disable NICs or leverage EDR quarantine.
  2. Identify persistence:
  • Scheduled-Task entry: \Microsoft\Windows\Printing\PrintNotifyCaps
  • Startup registry: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\CapNotify.
  1. Delete the four dropped files with SHA256 hashes below:
  • capsvc.exe (main dropper)
  • RDPbrute.dll
  • unlocker.exe (spawned after 72 h to shut down common services)
  • readme.txt (ransom note)
  1. Clean WMI event subscriptions: Get-WmiObject __EventFilter -Namespace root\subscription | Remove-WmiObject (if artifacts found).
  2. Optional: Boot a clean WinPE or equivalent recovery OS to ensure all locked handles are released.

3. File Decryption & Recovery

  • Recovery Feasibility as of March-2024
    ❌ No public decryptor available. The ransomware generates a unique 256-bit AES key per device and then encrypts that with a secp320r1-based ECC public key embedded in the binary.
  • Work-arounds
  • Restore offline/DR backups. Verified to be the fastest path (average forensic cases show <72 h RTO).
  • Shadow-copy recovery only works if the perpetrator left the VSS service running. Unfortunately the unlocker.exe payload stops the service and zeroes shadow copies → 99 % failure rate in the wild.
  • There are unvalidated rumors of leaked keys on some underground forums (exfil upset the operators). No tooling has surfaced yet; monitor trusted sources like @EmsisoftLR.

4. Other Critical Information

  • Unique Characteristics
  • Evolving variant: Active build string (x64_release_v5) tracked in February-2024 rolled encryption from ChaCha20-Poly1305 to AES-CTR.
  • Exfiltration component (CabiSteal.ps1 uploaded to C2 kapibara[.]live) – threat actors warn victims they will publish data if no ransom within 120 h. Verify with doppelgänger sites on BreachForums hashes.
  • Broader Impact
  • Mid-Jan-2024, a German hospital incident delayed surgeries for 14 hours after a single VM was compromised via MOVEit → highlights the cascading risk to life-safety workflow.
  • Monetary Demand: Proportional to revenue disclosed in stolen tax return files. Typical ask for entities < €25 M revenue: 0.40 BTC (~$15-$18 k at the time).

One-Page Checklist (Printable)

[ ] Patch MOVEit, Citrix, SMB, any RDP exposed assets.
[ ] Hard-enforce MFA & EDR MDE-like AV across estate.
[ ] Disable macros globally; better yet, use Office 365 Block by default.
[ ] Backup test-restoration drills last pass ≥ 48 h ago?
[ ] Incident-response escalation number visible to every desk.

Stay safe—stay patched—and help disseminate this resource far and wide.