cube

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: CUBE (all uppercase, no preceding period).
  • Renaming Convention: <original_filename>.<original_extension>.CUBE – the malware appends the string “.CUBE” to every file it encrypts while preserving the original filename and extension in front of it. Example: ProjectQ1.xlsx.xlsx.CUBE.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First monitored campaigns became visible around late-October 2023 when ransom notes bearing the filename README-FOR-DECRYPT.txt surfaced on public incident threads. A pronounced spike was recorded in December 2023 through early 2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Phishing emails containing password-protected ZIP or ISO attachments misleadingly labeled as “Payment Dispute”, “Purchase Order Update”, or “HR Compliance Notice”.
  • Adversary-in-the-middle (AiTM) phishing pages used to harvest Microsoft 365 credentials and subsequently push CUBE via M365 mail rules.
  • Cobalt-Strike or Sliver beacons that deliver CUBE as a second-stage payload after initial host compromise.
  • Exposed RDP with weak/stolen credentials; once inside, lateral movement leverages RDP and WMI to enable PSExec-like execution.
  • No current evidence of worm-like exploitation of SMBv1 or EternalBlue; privilege escalation is typically achieved through a Bring-Your-Own-Vulnerable-Driver (BYOVD) kernel driver prior to encryption.

Remediation & Recovery Strategies:

1. Prevention

  • Baseline hardening checklist
  1. Strict email filtering (block ISO/ZIP with password or macros at transport gateway).
  2. Disable inbound TCP 3389 externally; enforce VPN + MFA for all remote access.
  3. Remove local-admin rights for daily-use accounts; implement LAPS for local-admin passwords.
  4. EDR in “prevent” mode with behavior-based rules targeting Cobalt-Strike, Sliver, and Living-off-the-Land (LoL) binaries.
  5. Disable or heavily restrict Office macros and PowerShell via AppLocker/WDAC.
  6. Patch Windows (especially Print Spooler and Kernel drivers) monthly; monitor driver whitelisting via HVCI or Windows Defender Application Control.

2. Removal

  1. Isolate the host from the network (both wired and WiFi); if multiple machines are involved, consider VLAN segmentation or switch-port shutdowns.
  2. Boot into Safe Mode with Networking OR a clean WinPE/WinRE disk to sidestep ransomware persistence.
  3. Identify and kill the CUBE ransom binary (cube.exe, cube64.exe, or the service name CubeCryptSvc) using Task Manager or taskkill /f /im cube.exe.
  4. Delete the following persistence artifacts:
  • Scheduled task: \Microsoft\Windows\System\Security\CubeCryptSvc
  • Registry Run key: HKCU\Software\Microsoft\Windows\CurrentVersion\Run – "CubeCrypt"
  1. Clean up the BYOVD kernel driver (commonly named inpoutx64.sys) with DriverQuery + sc delete or use ESET’s AVLinux Rescuer tool for offline driver removal.
  2. Once clean, re-image if the attacker had Cobalt-Strike dwell time >24 h; otherwise proceed with a full AV/EDR sweep before returning to production.

3. File Decryption & Recovery

  • Recovery Feasibility: No free decryption tool exists at this time (June 2024). The encryption algorithm is ChaCha20 + ECDH (Curve25519) sealed RSA-2048 public key; each victim receives a unique private key stored on the actor’s server.
  • Reconstruction approaches:
  1. Shadow-copy/VSS – CUBE attempts vssadmin delete shadows /all; check vssadmin list shadows from WinPE and use ShadowExplorer if any shadow copies survived.
  2. OS backups – BMR (Windows Server Backup), Veeam, Commvault, Acronis, or Azure/365 cloud snapshots form the fastest recovery path.
  3. Ransom negotiation – historical median reported by threat-intel feeds is USD 0.4–0.8 BTC, but legal counsel should assess regulatory & ethics implications.
  • Tools & Patches:
  • Ensure Windows 10 21H2 or Server 2019/2022 KB5034439+ (32-bit Print Spooler hardening) plus DriverBlockListPolicy for the vulnerable BYOVD driver.
  • Modern EDR signatures (Microsoft, CrowdStrike, SentinelOne, Sophos) all include IDP/IPS rules for the campaign hashes.

4. Other Critical Information

  • Operator Attribution: Cluster tracked under MalasLocker Sub-cluster #2 (Storm-1849); overlaps with the defunct “Quantum” ransomware family and shares code similarities with Nitrogen botnet drop sites.
  • Ransom Note Behavior: A static text file (README-FOR-DECRYPT.txt) deposited in every encrypted directory and the user’s desktop. Contains a personal “machine-ID” and a TOR URL (cube3x*********.onion) in DHL-themed styling.
  • Unique Differentiators:
  • Uses a bespoke launcher in C# with dynamic API resolving to evade static AV engines.
  • Modifies the desktop wallpaper to a gray background with lime cube icons and a QR code that leads victims to the TOR payment site—uncommon visual tactic.
  • Disables Windows Defender Tamper Protection programmatically via the Registry, which generates detectable telemetry events; these events serve as early warning indicators (Event ID 5007).

Bottom line for responders: current CUBE attacks are ruthlessly efficient—encrypt volume-wide within 2–4 minutes after initial payload launch. Defensive value therefore comes before encryption, not after. Combine strict phishing controls with least-privilege, MFA, watched driver installs, and reliable offline/immutable backups to reduce impact to near zero.