cuba

[Content by Gemini 2.5]

Technical Breakdown – CUBA Ransomware (.cuba)

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: All successfully-encrypted files receive the exact extension .cuba appended to their original name (e.g., Invoice_2024.xlsx → Invoice_2024.xlsx.cuba).
  • Renaming Convention: No prefix is added; files keep their original base name plus the new extension. Occasionally, subsidiary droppers also insert an isolated HOW_TO_RESTORE_FILES.cuba.txt in every folder.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First samples were submitted to public repositories and CERT feeds in late February 2020. Activity spiked again in late 2021–2022 with notable campaigns against critical infrastructure and healthcare in North America and Europe.

3. Primary Attack Vectors

CUBA operates as a human-operated, double-extortion enterprise ransomware.

  • Exploitation Paths Commonly Observed:
  • RDP / RDP over VPN – lateral movement from compromised corporate credentials or brute-forced accounts.
  • Living-off-the-land binaries (e.g., certutil, PowerShell, PsExec, Windows BITS) for staging.
  • ProxyLogon/ProxyShell exploits on on-premise Microsoft Exchange servers to obtain initial foothold.
  • Veeam Backup & Replication vulnerability (CVE-2023-27532) abused to wipe or encrypt backup repositories.
  • ZeroLogon (CVE-2020-1472) on still-unpatched domain controllers to escalate privileges.
  • Phishing emails with weaponised ISO/RAR attachments containing BazarLoader or Cobalt Strike beacons to fetch the CUBA payload.

Remediation & Recovery Strategies

1. Prevention

  1. Zero-trust segmentation – VLAN segmentation for critical servers; isolate backup infrastructure.
  2. Patch discipline – Prioritise Exchange, ADCS, Veeam, and OS cumulative updates within 24–48 h of release.
  3. Disable RDP externally; enforce VPN gateways protected by MFA.
  4. Credential hygiene – Rotate all domain and local admin passwords upon any IOC; enforce 16-character minimum.
  5. Application allow-listing – Use Microsoft Defender Application Control or third-party equivalent to block unsigned binaries, including cuba.exe hashes (FeodoTracker list: SHA-256 09d12…a8e4).
  6. EDR + DNS filtering – Ensure EDR agents are installed and set to block TOR egress traffic. Block known CUBA C2 domains (e.g., kennarbranchdirector.com, www.analyzemainb[.]com).

2. Removal

Strict containment sequence recommended:

  1. Isolate the host (disable Wi-Fi NICs and unplug Ethernet).
  2. Collect forensic snapshots – acquire RAM and disk images before any reboot, if legal requirements oblige.
  3. Kill active processes – CUBA may spawn cuba.exe, net.exe, ntdsutil.exe, vssadmin.exe. Terminate via EDR or Safe Mode with Networking.
  4. Delete persistence artifacts:
  • Registry Run key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\SystemBC
  • Scheduled task: name varies (“NetworkHealthUpdater”).
  • Service entry: “PowerSync service” often used to disguise Cobalt-Strike.
  1. Remove secondary payloads – Cobalt-Strike beacon DLL drop under %APPDATA%\Oracle.
  2. Apply updates – Patch OS, Exchange, Veeam before returning to production.
  3. Rebuild/re-image domain controllers if TTPs included DCSync (unlikely but safest).

3. File Decryption & Recovery

  • Recovery Feasibility:
    NO public decryptor exists at this time; CUBA uses ChaCha20 + RSA-2048 asymmetric key wrapping. No flaws in the key handling logic have yet been discovered.
    Recovery pathways:
  1. Offline backups – in >60 % of analysed incidents, unaffected immutable / air-gapped backups saved organisations from ransom payment.
  2. Negotiation with attackers – risk vs. reward is board-level decision; the decryptor delivered has been observed to fail on fail-over clusters (restore from backups remains most reliable).
  3. Shadow-copy forensics – if attackers missed a volume shadow copy (rare but occurs in hybrid clouds), leverage Volume Shadow Explorer or vshadow.exe.
  • Essential Tools/Patches:
    • Microsoft Exchange server cumulative security updates (2023-03).
    • Veeam Backup & Replication 12.1 (or 11a + hot-fix KB4424 addressing CVE-2023-27532).
    • CrowdStrike / SentinelOne with kernel-level prevention tuned to block ChaCha20 file-IOP pattern.

4. Other Critical Information

  • Unique Characteristics:
  • Uses both Windows services and Linux variants (VMware ESXi).
  • Data-theft tactics employ the bespoke **“Cuba-Collect” exfiltration toolkit scanning for industrial control drawings (P&ID), PII, SAP credentials.
  • Encrypts VM-level backups first—especially VMDK, VHDX, Avamar, and Veeam .vbk files—before targeting user shares.
  • Broader Impact:
  • CUBA’s leak site (.onion) publicly posted data from >120 organisations, including 911 call centres and municipal water utilities (2022 US CISA alert AA22-335A).
  • Observed $60–70 M USD extorted across 2021-2023, according to OFAC advisories; some payments, once traced, triggered sanctions against actor wallets (15yM7…ae0fS).

Immediate step-through playbook: patch → backup-validation-check → network segmentation review → SOC tabletop to simulate CUBA TTPs.