ahegao - NTAPINSIGHT

Technical Breakdown

1. File Extension & Renaming Patterns

Confirmation of File Extension: .ahegao (The string is lowercase and is appended verbatim after the original file extension, e.g., Photo2024.jpg → Photo2024.jpg.ahegao)
Renaming Convention:
• Files keep their original name and first extension unchanged; .ahegao is simply tacked on at the end.
• No “original-file-ID-email.wallet” style pattern; the name remains human-readable.

2. Detection & Outbreak Timeline

Approximate Start Date/Period: First public sightings were recorded in mid-October 2021. Activity spikes were reported during late-Oct—early-Nov 2021, and occasional clusters still appear in 2024.

3. Primary Attack Vectors

Remediation & Recovery Strategies

1. Prevention (Top Priority)

| Action | Why it helps for Ahegao |
|—|—|
| Segment SMB via firewall ports 445/135/139 to servers only | It uses SMB later, not EternalBlue, but lateral scan still succeeds if open |
| Disable PowerShell v2 & JScript.vbs engines by GPO | Many droppers rely on those engines |
| Mail-gateway: strip ISO/ZIP (or isolate unknown macro files) | Most seed-builds arrive this way |
| Enforce application allow-lists w/ Windows Defender ASR rules | Stops unsigned .NET droppers in temp dirs |
| MFA lock-down on all RDP/SSH service ports | Credential-spray campaigns often initial entry |
| Remote PowerShell ExecutionPolicy: restricted, plus ConstrainedLanguage mode | Kills off-the-shelf PowerShell loader scripts |
| Comprehensive backup strategy with 3-2-1 rule (keep at least one copy offline) | Sole guaranteed recovery route (crypto keys are per-host AES-256) |

2. Infection Cleanup – Step-by-Step

| Step | Action & Notes |
|—|—|
| 1 | Isolate infected device immediately (pull LAN cable / disable wi-fi). |
| 2 | Identify running processes: look for random-name .exe (e.g., nsPSYXXW.exe, dkernaal.exe) in:
%LOCALAPPDATA%\Temp\, C:\Windows\Temp\, or %USERPROFILE%\.dotnet\. |
| 3 | Collect memory dump / full image, then power off (avoids further encryption). |
| 4 | Boot from Safe-Mode or WinPE USB, delete scheduled tasks:
schtasks /delete /tn "WindowsUpdates" /f
Registry: HKCU\Software\Microsoft\Windows\CurrentVersion\Run,
HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\StartupApproved\Run. |
| 5 | Run Microsoft Defender offline scan, then follow with reputable 2nd AV (ESET, Sophos, Kaspersky). |
| 6 | Check LAN mapped drives & remote servers—mount them read-only on a clean machine, scan before trusting. |

Automated tool: some security suites (Malwarebytes 4.6+, SentinelOne v22+) have signatures Mal/Ransom-GQ.ahegao.

3. File Decryption & Recovery

Recovery Feasibility: No free public decryption tool exists for Ahegao as of June-2024. Each encrypted file is individually ciphered with a victim-specific 256-bit AES key that is then encrypted by the attacker’s RSA-2048 public key. Both keys are uploaded to the malware C2 only.
Available Options:
• Backups (offline, immutable, Veeam replica, Microsoft Azure Immutable Blob, tape) are the only sure route.
• Volume Shadow Copies (VSS) are usually deleted automatically (vssadmin delete shadows /all /quiet). Restore-luck angle: Attacker did not purge System Protection backups on some Windows 7 images and network drives.
• Unencrypted temp copies left over in %TEMP%\nsXXX.tmp or %LOCALAPPDATA%\Packages\Microsoft.Microsoft…\AC\Temp can yield partial recovery (rare; depends on encryption-trigger timing).

4. Other Critical Information

Unique Characteristics
• Refuses to encrypt folders named C:\Program Files, C:\Windows, but does attack mapped network drives, SMB shares, and removable USB storage from those clean PCs.
• Drops a ransom-note HOW_TO_DECRYPT_FILES.txt in every affected directory; note contains a Tor chat URL and the wallet address.
• Embedded GIF image at top (“ahegao” anime meme) used as desktop wallpaper.
Wider Impact
• In 2021, Mexico & Spain public universities suffered variant Ahegao.ES-11-21, forcing one large hospital to divert oncology patients.
• Recent iterations (detected 2023-2024) bundled a Discord Spreading Module that scans %APPDATA%\discord\Local Storage to auto-send dropper executables via DMs of prior server members.

Essential Patches / Tools (check-list)

Remember: treat every newly discovered .ahegao sample as potentially evolved. Isolate, capture, and analyze, but do not connect decrypted systems to production until all lateral accounts and emails have been reset.

Stay safe, patch aggressively, and practice immutable backups!