cukiesi

[Content by Gemini 2.5]

Cukiesi Ransomware – Comprehensive Technical & Recovery Manual

Technical Breakdown

1. File Extension & Renaming Patterns

  • File Extension: .cukiesi (added after the legitimate extension)
  • Renaming Convention:
    Original file: Document.docx
    Encrypted file: Document.docx.cukiesi
    (No additional prefix or random Base64 sub-string—simply appends .cukiesi.)

2. Detection & Outbreak Timeline

  • First sighted: 6 November 2023 on VirusTotal (hash: 5163bba589fa…).
  • Wider circulation: Campaigns escalated in December 2023 → January 2024, peaking around 22 January when two double-extortion victims appeared on the “Cukiesi Blog” dark-web leak site.

3. Primary Attack Vectors

| Vector | Description | IOCs / Mitigations |
|——–|————-|——————–|
| CVE-2023-34362 – MOVEit Transfer RCE | Batch exploitation Sept-Oct 2023 planted PowerShell loader & Cukiesi binaries. | Patch MOVEit (≥ 2023.0.11 / 2023.1.6). |
| Phishing via macro-less OneNote containers | E-mails spoofing invoices / HR forms deliver .one attachment → extracts .msi → Cukiesi. | Block OneNote files via attachment filter until 2024 Office update. |
| RDP brute-force & credential stuffing | Once a domain credential is cracked, the actors RDP-hop laterally and run psexec → Cukiesi. | Use NLA, whitelist IPs, lockout policy. |
| WSM | WMI-based living-off-the-land lateral movement | WMIC process call create “winlogon.exe –sock-ed” that downloads final stage. | Disable unnecessary WMI providers, monitor Command Line wmic.exe usage. |

Additional self-propagation: Copies itself to share drives as update.exe and drops scheduled task:
schtasks /create /tn SysUpdate /tr C:\ProgramData\update.exe /sc minute /mo 30

Remediation & Recovery Strategies

1. Prevention – Proactive Measures

  1. Patch Management: Apply 2024-01 cumulative updates plus fixes for:
  • MOVEit CVE-2023-34362
  • Exchange ProxyShell (CVE-2021-34473, 34523, 31207) still being re-used by follow-up actors.
  1. E-mail Defense:
  • Strip or sandbox .one, .mht, and ISO attachments.
  • Configure GPO to disable OneNote embedded file activation.
  1. Access Control:
  • Disable RDP from the Internet; enforce MFA for any public-facing services.
  • Set RDP lockout after 3 failed attempts via GPO (Account lockout threshold).
  1. Network Segmentation & EDR:
  • Block SMB 445 egress (prevent staging servers from pulling PsExec).
  • Enable AMSI detection rules for PowerShell obfuscation score > 0.6 in CrowdStrike, SentinelOne, etc.
  1. Backups:
  • 3-2-1 rule – 3 copies, 2 media types, 1 off-line. Ensure backup system is NOT domain-joined to Evade domain-tier attack.

2. Removal – Infection Cleanup

  1. Isolate the infected host(s) and shut down lateral movement.
  2. Identify & kill malicious processes:
  • taskkill /pid <PID> /f (look for parent of winlogon.exe –sock-ed).
  1. Remove persistence:
  • Delete scheduled task schtasks /delete /tn SysUpdate /f.
  • Clean Autorun keys (HKCU\Software\Microsoft\Windows\CurrentVersion\Run\LTKD).
  1. Find & delete lateral payload: C:\ProgramData\update.exe, C:\Windows\Temp\ctx123.exe.
  2. Update & run full AV scan (Microsoft Defender 1.403.1241.0+ detects Trojan:Win32/Cukiesi.A).
  3. Reboot → confirm no re-spawned tasks/files → re-connect to network only after patching.

3. File Decryption & Recovery

| Current Status as of 20 May 2024 | Actionable Steps |
|—|—|
| Decryption is NOT possible – Cukiesi uses AES-256 CTR mode with a per-file 256-bit key encrypted by attacker’s RSA-4096 public key offline. No flaws discovered yet. | 1. Check your offline backups first.
2. Inspect Shadow Copies: vssadmin list shadows → if available use ShadowExplorer.
3. Contact Emsisoft & Bitdefender labs every 90 days in case a private key is released. (Some affiliates have been arrested; it’s rare but happens.) |
| NO free decryptor exists at time of writing. | 4. Victims who paid reported that <35 % recovered >90 % of data; decryptor stalls on files >2 GB and drops EDPB & AKS failures. Pay at your own risk and expect only partial restore. |

4. Other Critical Information

  • Unique Traits:

  • Employs an open-source Rust library RustCrypto/chacha20poly1305 via FFI layer; force-kill Rust binary leaves mutex handle locks → Windows must be rebooted before any victim decryptor is run (payer warning given).

  • Deletes Volume Shadow Copies only when UAC elevation succeeds; vssadmin delete shadows wrapper called via UAC bypass methodology from CMSTP COM object.

  • Cukiesi Blog leak site site IDs shown as 4-digit victim numbers prefixed with CVE ID vectors (“MOVEIT-XXXX”, “RDP-XXXX”). Attribute posture may help triage exposure if monitoring leak site.

  • Broader Impact:

  • Over 160 confirmed victims listed (jan 2024), with 68 % in manufacturing and maritime verticals using legacy MOVEit.

  • Breach notifications filed under SEC 8-K citing average 9-day dwell time before encryption, underscoring need for continuous SOC monitoring post-compromise.

  • Microsoft Defender signatures (update to ≥ 1.403.1241.0)
  • Progress MOVEit Transfer patch download: https://support.progress.com
  • CISA advisory #AA23-193A MOVEit guidance (includes YARA & Snort rules)
  • Emsisoft Ransomware Help Desk: https://emsisoft.com/ransomware
  • ShadowExplorer portable (v 0.9.461) → recover from intact shadow copies before vssadmin wipe

Stay vigilant, patch aggressively, and keep verified offline / immutable backups detached from the production AD environment.