cryeye

[Content by Gemini 2.5]

Technical Breakdown: CryEye Ransomware

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .cryeye (in lower-case, appended after the final dot of the original file name).
  • Renaming Convention:
    [original_name].[original_extension].cryeye. Example: Spreadsheet_Q4.xlsx becomes Spreadsheet_Q4.xlsx.cryeye.
    No preceding e-mail address or random string, which differs from double-ext families like “.id-12345.[address].cryeye”.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First seen in wild mid-April 2022. A sharp spike occurred during May–October 2022 before taping off, likely because decryptor tooling was released.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Phishing e-mails with password-protected ZIP attachments (themes: DHL/UPS fake invoices, IRS refund forms).
  • RDP brute-force or previously sold corporate RDP credentials from underground marketplaces. Once inside, WMI/PsExec used for lateral movement.
  • Exploitation of Fortinet CVE-2018-13379 (SSL VPN leak) followed by Cobalt-Strike beacon deployment, then CryEye payload.
  • Drive-by downloads via malicious ads that drop CryEye disguised as kmsauto.exe or similar cracking tools.
  • No indication (so far) of EternalBlue or SMBv1 exploitation.

Remediation & Recovery Strategies:

1. Prevention

  1. Disable direct RDP exposure on TCP 3389; enforce RDP gateway / VPN with MFA.
  2. Exchange/MS365 mail filters: reject encrypted ZIP containing executables or LNKs.
  3. Keep Fortinet, VPN appliances, and Veeam/VMware ESXi/VCSA (frequently hit for lateral moves) fully patched (includes CVE-2018-13379, 2022-37042, etc.).
  4. Segment networks; restrict SMB/WMI/PsExec between departments using Windows Firewall GPOs.
  5. Maintain multiple offline/offsite backups with 3-2-1 rule (minimum one copy that is air-gapped / WORM). Verify backup integrity monthly.

2. Removal

  1. Physical network isolation of suspected hosts to curb lateral propagation.
  2. Disable scheduled tasks / Run keys:
    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\ – remove any randomly-named key pointing to %APPDATA%\<uuid>\<random>.exe.
  3. Kill living-off-the-land processes (vssadmin delete shadows), then reboot into Safe Mode w/ Networking.
  4. Run a reputable anti-malware scanner (Malwarebytes 4.x, Bitdefender Ransomware Remediation, Sophos HitmanPro) to quarantine:
  • %APPDATA% payload & the dropped PowerShell or BAT pivot script.
  1. Mount affected drives as read-only on a clean, dedicated PC; run chkdsk post-cleanup to repair NTFS journaling issues before recovery.

3. File Decryption & Recovery

  • Recovery Feasibility: YES, decrypter available.
    CryEye uses XChaCha20-Poly1305 – a strong but not ransom-key-hardened scheme. Researchers at ElevenPaths/Telefónica released an offline CryEye Decryptor on 2022-07-12.
  • How to use:
  1. Download CryEyeDecryptor-v1.2.exe directly from https://github.com/ElevenPaths/CryEyeTools/releases (SHA-256: 4b0ae8844b8027970b5e59320c984536f1b4a5e03c8d7a9acd325a0840f46192).
  2. Admin-run from a clean computer or from WinPE USB/USBDisk—never on the infected OS.
  3. Provide:
    • folder containing any intact copy of the same file BEFORE encryption (pair-wise original & sample) – tool derives per-file key, then does full restore.
  4. Supply -l to log mode; review cryeye.log for any unreadable files (rare).
  • No impact if you wipe the VSS shadow copies; keys never transit to C2 servers.

No payment necessary.

4. Other Critical Information

  • Unique Characteristics:
  • Executes vssadmin delete shadows /all /Quiet before encryption – illustrating destructive intent but still recoverable via external backup or the decrypter—hence backups are vital.
  • Drops a personal readme: README_DECRYPT.txt containing a ProtonMail address and BTC wallet ending in “AHv”. Wallet analysis yields mostly empty balances after law-enforcement intervention (December 2022).
  • Uses adjacent-name for encrypted files only (does NOT inject ransom note widgets into GUI).
  • Broader Impact:
  • Hit medium-sized healthcare & logistic orgs in LATAM + Europe; temporary ESXi snapshot purge made VM shutdown non-bootable, extending downtime from hours to days.
  • CryEye indirectly triggered CISA alert AA22-227A spotlighting commodity VPN exploitation.

Must-Have Resources & Patches

  1. Decryptor tool (see §3) → keep offline copy.
  2. Update Fortinet FortiOS (≥ 7.0.10 or 6.2.11 patch) – mitigates SSL-VPN leak.
  3. Windows patches (optional but prudent): all released after KB5014754 provide deeper SMB protection; not directly CryEye relevant but helps lateral threats.
  4. Rapid7, LUARM, or Qualys network scans to detect open RDP: search services on TCP 3389 + check for presence of msrdp misconfigurations.

Stay vigilant—cryeye is mostly neutralised, yet its family of VPN-exploited strains keeps mutating.