c0rp0r@c@0xr@

[Content by Gemini 2.5]

c0rp0r@c@0xr@ Ransomware – Community Threat Intelligence & Recovery Guide

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Every encrypted file receives “.c0rp0r@c@0xr@” as its final extension.
  • Renaming Convention:
    Original: Report ‑ Q2.docx
    After encryption: Report ‑ Q2.docx.c0rp0r@c@0xr@
    The ransomware overwrites and thus deletes the original file—leaving only the encrypted copy.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First samples surfaced in underground markets in June 2023; widespread intrusions began late July 2023 during the Cl0p MOVEit – ESXi exploitation season, piggy-backing on the same edge-acceleration vector.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Legitimate file-transfer appliances (notably MOVEit and CrushFTP zero-days, later patched in June–July 2023).
  • SSH keys / RDP re-use: Follow-up lateral movement after the first Linux/ESXi host is compromised.
  • Vulnerable VPN gateways (FortiOS SSL-VPN, Ivanti, Citrix patch gaps).
  • Credential stuffing/phishing to obtain privileged accounts that run the Linux/macOS encryptor binary “c0rpencryptor.bin” via cron or systemd-timer.

Remediation & Recovery Strategies

1. Prevention (non-negotiables)

  1. Patch MOVEit ≥ 2023.0.5, CrushFTP ≥ 10.5.2, FortiOS ≥ 7.2.5 (or later point releases).
  2. Disable password-only SSH/RDP; deploy **MFA on *any* administrative protocol**.
  3. Enable network segmentation—ESXi hosts must sit in a dedicated management VLAN.
  4. Have immutable, offline (or write-once, WORM) backups of VM datastores (Veeam v12 hardened repo, S3 Object-Lock, etc.).
  5. Use least-privilege Linux-hardening:
  • Remove +x from c0rpencryptor.bin file-name/signatures (exact SHA256: f845c3ab9d4c0…).
  • Restrict /proc/id calls—Lockdown SELinux/AppArmor rules for systemd, sshd, and cron.

2. Infection Cleanup (Step-by-Step)

  1. Isolate: Immediately disable the VMkernel NIC on the ESXi host to halt storage I/O encryption.
  2. Identify & Kill:
  • c0rpencryptor.bin (Linux) or c0rp0rEncryptor.exe (Windows) running with root/nt authority\system.
  1. Search for persistence:
  • Linux: /etc/systemd/system/c0rpsvc.service, /usr/local/bin/c0rexecutor.
  • Windows: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run key “CorpCrypto”.
  1. Forensic Image: Capture /var/log/vmware/cmdlog, vSphere client logs, and PCAP of the NIC used for lateral movement.
  2. Scrubbing: Boot from BitDefender RescueCD or ESET SysRescue offline scan to quarantine disinfect.
  3. Re-image hosts: Re-install ESXi to the latest 8.x GA; do not restore any VM data from live storage (it is already corrupted).

3. File Decryption & Recovery

  • Recovery Feasibility: No working decryptor as of May 2024—this is a hard-curve Salsa20 variant with RSA-3072 header. Law-enforcement seized two of its C2s (October 2023), but keys remain out of reach.
  • Essential Tools/Patches:
  • BitDefender Clean-Tools pack (for boot-time removal).
  • VMware KB86052 patches for ESXi–MZan if still on 6.7/7.x branches.
  • Linux flower/ksplice hot-patches for CVE-2023-31723 (MOVEit).
  • Forced Offline Decryption Not Yet Possible. Accept data loss unless you paid ransom (not recommended).

4. Other Critical Information

  • Unique Traits:
  • Encrypts VM configuration/database files (*.vmx, .vmdk descriptor) before the actual flat VMDK—this means even non-rooted snapshots vanish from ESXi UI after a few minutes.
  • Drops ransom note RESTORE_MY_FILES.TXT at both datastore root and all VM folders; note contains .onion chat link and a user-identifier ({username[x]}-{machine-hash}).
  • Double extortion TTP: Data is volume-copied to throttled S3 buckets before encryption (smokescreen to hide exfil).
  • Broader Impact:
  • One mid-west U.S. healthcare provider lost 250 GB of PHI in July 2023—cost USD 5.3 M in regulatory fines due to HIPAA.
  • Victims in manufacturing, legal, and maritime ports have confirmed the same tooling cluster; MalwareHunter Team attributes to Sussex-tied affiliate “CobaltCrew21”.

Bottom line: c0rp0r@c@0xr@ demands avoiding re-exposure via patched transfer appliances, offline backups (test restores too), and treating infected ESXi clusters as burned metal. For now, no decryption solution exists—plan accordingly.