cobain

[Content by Gemini 2.5]

Cobain Ransomware – Community Resource Guide

(ext .cobain)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation: Files encrypted by this strain receive the exact suffix “.cobain”.
  • Renaming Convention: Original name + a 5–8 character pseudo-random string + “.cobain”
    Example: Quarterly_Finance_Q4.xlsx ➜ Quarterly_Finance_Q4.xlsx.H71k9.cobain

2. Detection & Outbreak Timeline

  • First public sightings: Early-December 2022.
  • Wider active propagation waves: March & July 2023, continuing with smaller surges into 2024.

3. Primary Attack Vectors

| Method | Details | Notable Examples |
|——–|———|——————|
| Phishing with malicious ZIP archives | E-mails disguised as invoices/HR alerts with password-protected ZIP containing an ISO or MSI. | “Payment-Remittance”, “Salary-increase-2024-Q3” subjects |
| Exploited public-facing web servers / VPNs | Hits on Apache Log4Shell (CVE-2021-44228), Fortinet SSL-VPN (CVE-2022-42475) and exposed ColdFusion. | Rapid mass-infection of SMBs running outdated Confluence/Jira in May 2023. |
| Cracked RDP sessions | Brute-force or purchased credential lists → RDP exposure on TCP/3389. | Forums thread “RDP 2023 dump – free list for Cobain” pop-up February 2024. |
| Malvertising via fake software updaters/bridges | Dropper posing as Chrome/Firefox update or KMS activator delivering Cobain stage 2. | Tracked on “nulledGFX[.]com” distributions. |

Remediation & Recovery Strategies

1. Prevention

  1. Immediate patching:
    • Log4j 2.16, FortiOS 7.2.3/7.0.10+, MS015-011 for SMB (block EternalBlue).
    • Keep Adobe ColdFusion, Atlassian, WordPress, remote-access software fully updated.
  2. Hardening:
    • Disable SMBv1 across domain.
    • Enforce Multi-Factor Authentication (MFA) on every VPN/RDP gateway.
    • Use an allow-list application-control policy (e.g., AppLocker / WDAC).
  3. Security stack:
    • EDR > CrowdStrike Falcon, SentinelOne, Sophos Central – configure behavioral rule “inter-process memory injection + Cobain extension list” for early detection.
    • Network segmentation and logging (Sysmon rules 1, 11, 13).
  4. Offline, tested backups (3-2-1 rule) with periodic restore drills.

2. Removal

  1. Isolate the infected machine(s): pull network cable, disable Wi-Fi/Bluetooth.
  2. Boot into Windows Safe-Mode or spin up a Linux-based live disk:
    a. Identify the running Cobain dropper (typical names: ihost.exe, ms-cortana-1284c9.exe, SysCollWin.exe).
    b. Kill processes, neutralize persistence:
    • %APPDATA%\Roaming\ & ProgramData folders.
    • Run & RunOnce keys referencing random *.exe.
  3. Scan with reputable AV/EDR (Malwarebytes, ESET, Windows Defender offline).
  4. Patch and reboot → verify extension-filtering rules to block new executions.

3. File Decryption & Recovery

| Status | Explanation |
|——–|————-|
| No working decryptor at this time. | Cobain uses a hybrid ChaCha20 + RSA-4096 schema with per-file keys encrypted by an adversary-controlled RSA key pair. No publicly released private master key. |
| Possible work-arounds | |
| – Shadow-copy check: vssadmin list shadows – if the ransomware failed to wipe restore points, use ShadowExplorer or Windows Previous Versions. |
| – Volume-level recovery: PhotoRec or Rundelete on unencrypted drive images may recover parts of large media. |
| – If you maintain offline/cloud backups, create a checksum-verified clone and restore clean data after wiping artifacts (above). |

4. Other Critical Information

  • Encryption behavior specifics:
    – Drops “+++HOWTORETURNFILES_###.txt” inside every folder.
    – Skips %WINDIR%, %SystemRoot%, boot directory, MongoDB database files (to keep host stable while ransom negotiations).
  • “Double-extortion”:
    – Cobain operators run a Tor-based leak site “cobaindataleaks.onion”. Stolen data exfiltrated via Mega, AnonFiles & IcedId loaders prior to encryption.
  • Suspected lineage: Shares code overlap with ransomware-as-a-service family “ALPHV” (a.k.a. “BlackCat”) – same affiliate panel UI and obfuscation style in later samples.
  • Geography: Concentrated on English- and Spanish-speaking targets (US, Canada, Brazil, Spain).
  • Insurance & negotiation trend: Initial ransom usually 2–8 % of annual revenue; affiliates often accept 30–50 % discounts if data appears unusable/low value. Still not recommended – pay without a guarantee.

Immediate checklist (print/save):
☐ Disconnect → identify Cobain process & persistence
☐ Patch relevant CVEs immediately on all machines
☐ Review backup scope & restore plans
☐ Notify SOC, cyber-insurer, and law-enforcement (FBI IC3 report)

Staying patched and employing robust offline backups remain the strongest defense against Cobain.