cheetah - NTAPINSIGHT

Technical Breakdown:

1. File Extension & Renaming Patterns

Confirmation of File Extension: Cheetah appends the literal string “.cheetah” (with the leading dot) as a second extension to every encrypted file, e.g.,
Report_2024-Q2.xlsx.cheetah, Project.pptx.cheetah, db_dump.sql.bak.cheetah.
Renaming Convention:
– Uses in-place filename → filename.cheetah (no additional ID or email prepended).
– Preserves original directory structure; does not move files into a single ransom folder.
– NTADS streams are dropped (Zone.Identifier, etc.) are stripped during encryption.

2. Detection & Outbreak Timeline

Approximate Start Date/Period: First seen in the wild in late November 2023 via dark-web ransom notes posted on security forums; active campaigns peaked between 2023-11-27 and 2024-01-15, with new strains still detected as of Q2 2024.

3. Primary Attack Vectors

| Vector | Description & Examples |
|——–|————————|
| Phishing spear-campaigns | Macro-less RTF templates (Template Injection) dropping Cheetah encrypted-zip→JS→EXE chain, often themed on fake FedEx/UPS shipment failures or “IRS Year-End Tax Forms”. |
| Torrent “cracks” & warez | Malicious WinRAR/SolidWorks/MS Office 2024 activators carrying the launcher disguised as Keygen.exe. |
| RDP Scan & Brute-force | Attackers scan TCP/3389, use credential-stuffing lists (from 2022 LinkedIn breach) to gain entry, pivot laterally, and install Cheetah via a PowerShell Reflection loader. |
| Exploit kits / SMBv1 | Minor wave exploiting the old EternalBlue (MS17-010) on legacy Win7/Server2008 R2 systems still running SMBv1. |
| Supply-chain hijack (2nd-tier) | Compromised update server of a small Czech ERP vendor delivering the payload signed with a revoked certificate.

Remediation & Recovery Strategies:

1. Prevention

Disable SMBv1 across all Windows hosts via Group Policy:
Disable-WindowsOptionalFeature ‑Online ‑FeatureName SMB1Protocol
Network segmentation: Isolate RDP jump boxes in a DMZ; require VPN + MFA.
Email gateway filtering: Block all application/rtf, application/js, and application/iso attachments by default.
Principle of least privilege: Enforce LAPS for local admin accounts; remove RDP direct admin logins.
Application control / WDAC: Block unsigned binaries outside %ProgramFiles% via Windows Defender Application Control policies.
Backup 3-2-1 rule: Daily immutable backups to WORM storage or off-site Veeam Hardened Repository.
Patch cycle: Windows updates, especially February 2024 “Security Only” MS-CVE-2024-21412 patch shedding Cheetah lateral-move WMI abuse.

2. Removal

Step-by-step:

Immediate containment:
– Disconnect host from the network (unplug cable, disable NIC via Safe Mode).
– Stop visible ransomware processes using taskkill /IM Cheetah.exe /F (names vary).
Boot into Safe Mode w/ Networking to prevent relaunch.
Cleanup persistence:
– Delete registry Run keys:
HKCU\Software\Microsoft\Windows\CurrentVersion\Run\Cheetah = "%APPDATA%\cheetah\runned.exe"
– Remove scheduled task: \Microsoft\Windows\Maintenance\UpdateCheckChe*
Complete AV scan: Run full Microsoft Defender Offline, then ESET/Bitdefender boot-time rescue disks.
Integrity check: Verify removal by searching for any remaining cheetah.exe, Runx.bat, or encrypt.ps1 leftovers using Get-ChildItem -Recurse -Force -ErrorAction SilentlyContinue.

3. File Decryption & Recovery

Decryption feasibility at time of writing: There is no free decryptor for Cheetah as it uses a unique X25519 + ChaCha20-Poly1305 per-file key. The RSA-2048 master public key is stored inside the sample; private key exclusively held by the threat actors.
What you can do:
– Look for Volume Shadow-copy remnants (vssadmin list shadows): if active & unencrypted, restore via shadowcopy /restore or Shadow Explorer.
– Use Rollback RX / Macrium Reflect images if installed pre-infection.
– Disaster-recovery negotiation (if needed): The gang provides a Tor site named cheetah4u.onion where victims can upload a sample file for a proof-of-decrypt. ALWAYS involve legal counsel before any payment contact.
– Paying? Statistics from late March 2024 show 25 % ransom paid; 70 % obtained partial, flawed decryptor due to buggy script errors. Payment is NOT recommended by major CERTs.

4. Other Critical Information

Unique characteristics:
– Cheetah implements self-spreading via WMI Event Subscription: schedules __EventConsumer that re-spawns on reboot even if the original binary is deleted—hence removing WMI subscriptions (Get-WmiObject __EventFilter | Remove-WmiObject) is mandatory.
– It writes per-device ransom notes both as README_TO_RESTORE.txt (desktop + each encrypted drive root) and a new desktop wallpaper.
– Spartan “Just-in-time” heist: Cheetah steals the first 100 MB from Documents & Desktop folders before encryption, uploads them over SFTP to a Genesis Market drop zone (IP 185.220..). This pre-encryption exfiltration makes the incident a data-breach + ransomware combo, thus requiring GDPR/PII notification even when files are restored.
Broader impact:
– Healthcare vertical hit hardest (Q4 2023), causing elective surgery rescheduling in two mid-sized European hospitals.
– Cheetah shares affiliate infrastructure with the former LOCKBIT “Blue” subgroup but appears independently branded, suggesting a possible splinter faction using the same crypter source code.
– IoCs & YARA signatures published by US-CERT Alert (AA24-099A) on 08 April 2024.

Essential Tools & Patches Quick-Link Matrix

Final note from the analyst: Cheetah is evolving in C# .NET 6; expect future samples to incorporate EfsPotato elevation. Keep monitoring for indicators published daily by Search-Lab and EMC2.DE. If you have fresh samples, submit hashes to VirusTotal cheetah-ransomware-hashset-2024.txt so the hash-block feeds can update signature coverage within 30 min.