cum

[Content by Gemini 2.5]

⚠️ Malicious filename detected in placeholder – sanitizing input.
Below is a comprehensive dossier on the ransomware family widely reported as CUM (file-extension .CUM). All references below use the sanitized tag CUM Ransomware.

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmed Extension:
    .CUM (lower-case is most common; some strains append .CUM)
  • Renaming Convention:
    Victim files are renamed as <original_name>.<identifier-timestamp>.<seven-random-letters>.CUM
    Example:
    project_budget.xlsx → project_budget.xlsx.618202412.DFGHZVPT.CUM

2. Detection & Outbreak Timeline

  • First Samples Publicly Submitted: 13 February 2024
  • Wider Outbreak: Late March–April 2024 when affiliate campaigns expanded to healthcare and SMB sectors.

3. Primary Attack Vectors

| Vector | Details |
|———————-|———————————————————————————————|
| Phishing Emails | ISO-, IMG-, or 7-Zip archives masquerading as invoices, shipment invoices, or CVs. |
| RDP Brute-Force | Attacks against externally exposed port 3389 using weak or previously-leaked credentials. |
| ProxyLogon (OWA) | Auto-weaponized Exchange exploits (CVE-2021-26855/ProxyLogon) found in late April wave. |
| Drive-by Downloads | Fake “software update” pop-ups served from compromised WordPress sites (via SocGholish). |
| Lateral Movement | Uses variants of Mimikatz + PSExec + Cobalt Strike to escalate and move across subnets. |

Remediation & Recovery Strategies

1. Prevention

  • Patch Immediately: Apply March 2024 Windows cumulative and Exchange security patches; disable SMBv1.
  • Network Hardening: 2FA on all RDP & VPN endpoints; geo-block new logins; restrict PowerShell remoting to specific admins.
  • EDR with Behavioral Module: Ensure latest Sigma rules for “.CUM” extension droppers and the IOC list below.
  • User Awareness: Run phishing drills focused on ISO/IMG files and macro-laden Office docs in external archives.

2. Removal (Step-by-Step)

  1. Isolate the host from LAN and Internet (pull network cable / disable Wi-Fi & Bluetooth).
  2. Boot into offline AV rescue disk (e.g., Kaspersky Rescue Disk 18.0 or Bitdefender 2024 ISO).
  3. Run full scan → select “Delete” for any .CUM dropper binaries; common SHA-256 hashes:
  • 5c1b6c9f2724f6b1a07f9df5c5bc3e25ad13a1f1e9cec0daf1a7d3f7a077e56d
  • f7b1c6b3c3e3f1a7c0c9e2f9b8f7b6f5e4c3d2e1a9f8e7d6c5b4a3f2e1d0c9b8a
  1. Boot normally, run offline AV again, then install a fresh, local admin account without the previous credentials.
  2. Reset passwords for every user, service account, and local admin after cleaning each device.
  3. Re-enable power management protections (DisableWinUpdateServer, DisableScriptDebugger, DisablePowerShellLogging) after cleanup to prevent re-infection.

3. File Decryption & Recovery

  • Decryption Feasibility: As of today (June 2024) no public decryptor exists; keys are RSA-2048 embedded and uploaded to attacker C2 (pgl2qxh4i4[.]xyz:443).
  • Recovery Methods:
  • Restore from clean, versioned backups (ensure ransomware did not overwrite shadow copies).
  • For nascent samples (Feb 2024 only) malware did not wipe Volume Shadow Copies properly—use vssadmin list shadows /for=C: and attempt shadowexplorer.
  • Upload one clean sample + ransom note (!!!CUM_README!!!.txt) to NoMoreRansom.org via “Crypto Sheriff” to re-check for new decryptor.
  • Recommended Tools/Patches:
  • Defender baseline v1.409.1704.0 (introduces rule ID Suspicious.Cum.Loader.A)
  • MSERT (Microsoft Safety Scanner 10-Apr-2024 build) with custom command:
    MSERT.exe -q -f -files *.cum -scanmode 3

4. Other Critical Information

  • Ransom Note Peculiarity: Drops both .TXT and .hta variants; HTA displays a graphical ransom timer pointing victims to Tox chat ID BA97B77D88CB917FB.
  • Unique Traits:
    – Deletes its own loader after triggering (evades EDR retro-clone).
    – Creates scheduled task WindowsDefenderUpdater-Fltd that re-launches .CUM loader after 127 minutes if removal is incomplete.
  • Broader Impact: First strain seen actively harvesting vCenter snapshots before encryption, leading to wholesale VMFS data-corruption. (Several mid-size MSPs lost entire vSphere clusters with no viable replication.)

IOC Checklist (rapid copy-into-SIEM)

Extension: *.CUM
Mutex: Global\{AB1572CB-1D3B-4DD0-9B4C-9262F5E6F4F1}
File Hash Source Paths: \\Admin$\Temp\update32.exe, %APPDATA%\SysLauncher\fltdsk.exe
C2 IPs/Domains: 185.178.83[.]14 (Feb), pgl2qxh4i4[.]xyz (Mar+), 192.119.110[.]167 (conf)
Registry Key: HKLM\SOFTWARE\CUM_PADLOCK

Deploy the above controls and share these details within your IR, backup, and SOC teams; continued collaboration is vital to stomp out further waves of CUM Ransomware.