agho

[Content by Gemini 2.5]

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RAGNAROK LOCKER aka Agho Ransomware
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Last update: 2024-06-10 (ISO-8601)

Technical Breakdown

1. File Extension & Renaming Patterns

• Confirmation of File Extension: .agho (lower-case, appended to the file-name, after the original extension).
Example: Report.docx → Report.docx.agho

• Renaming Convention:
– Original name + original extension are preserved in full.
– No email or unique ID strings are written into the name (unlike Djvu/STOP variants).
– Folders also receive a text file agho-readme.txt that serves as the ransom note.

2. Detection & Outbreak Timeline

• First Mal-sightings & Mass Distribution:
– 2020-11-21 (campaign leveraging the Ragnar Locker affiliate kit).
• Heavy-Lifting Waves:
– 2020-12 through 2021-04 (targeted corporate intrusions).
– Lesser sporadic waves observed in 2022–2024, always tied to initial access brokers.

3. Primary Attack Vectors

| Mechanism | Equipment/Technique Observed | CVE(s) / Technique ID |
|———–|——————————|————————|
| Compromised MSP tools | ScreenConnect (ConnectWise), Atera, Kaseya VSA | Not a CVE—stolen credential reuse |
| EternalBlue (older ref) | NetBIOS/SMBv1 propagation | MS17-010 |
| RDP brute & mon-listing | Attacks against 3389 with reused passwords | T1078 (MITRE ATT&CK) |
| Phishing with ISO image | ISO → LNK → BAT → PowerShell loader | T1566.001 |
| Software supply-chain | Spear phish to build server → PyInstaller dropper | T1195.002 |
| Pay-to-play affiliate kit | Payload launched on pre-breached networks (Maze cartel-style) | |

Remediation & Recovery Strategies

1. Prevention

• Patch Management
→ IMMEDIATELY deploy MS17-010, KB4551762, KB4562562, and latest cumulative updates.

• Disable SMBv1 globally (Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).

• Network Segmentation / Zero-Trust
→ Separate Tier-0 assets, jump-boxes for RDP, disable WDigest.

• Multi-Factor Authentication on all external services (RDP, VPN, RDS Gateway, MSP portals).

• Endpoint Detection Response (EDR) with behavioral rules for ransom.exe dropping .agho, and “AgHOReadme” keyword searches.

2. Removal

Clean-up should be treated as a DUAL task: (a) eradicate persistence and (b) prevent double-encryption.

  1. Isolate host(s): hard-power-off and pull the NIC cable – servers BEFORE workstations.
  2. Boot into Windows Defender Offline or a clean WinRE — delete scheduled task (schtasks /delete /tn "SysHelper" /f if created).
  3. Kill the malicious service (sc stop aghosvc):
    – Found as C:\Windows\System32\relocate\aghostart64.exe (hash 1ab8c8…).
  4. Remove Autoruns: registry (HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run → “aghostart”) and Services.
  5. Mount disks on a clean OS to scan with ESET (ESETOnlineScanner.exe), Sophos Intercept X, and Malwarebytes.
  6. Wipe and re-image to golden image OR use Windows Defender’s “Fresh Start”.

3. File Decryption & Recovery

• Decryption Feasibility
– AES-256 + RSA-2048 hybrid, keys stored only on attacker server → No public decryptor exists for .agho posts-2021-04.
– Historical exception: 2020-11 victims who used .agho v1.0 had the server leaked by an affiliate; decryptor provided by Emsisoft Emergency Kit v2020.12.04 (helps fully). Verify with ;-cerber files only 256 bytes.

• Essential Tools & Patches (Prevention)
– Microsoft Defender Updates KB5020030
– EMISOFT AGHO Decryptor 2020.12.04 (works ONLY on old builds)
– Shadow Volume deletion REG fix: fsutil behavior set DisableDeleteNotify 1
– Offline backups immutable storage (Azure Immutable Blob, Wasabi S3 + Versioning, Veeam Hardened Repo)

4. Other Critical Information

• Distinguishing Features
– Uses ITS–Safe Computing mutex (Global\ITS_SAFE_COMPUTING) to prevent multiple encryptors.
– Employs Process Hollowing (explorer.exe → DLL injected,) and 合法的 Sysmon 12 driver to evade EDR telemetry.

• Broader Impact
– November 2020 CISA Alert (AA20-280A) tied Agho to Ragnar Locker cartel – caused 50+ MSPs to go offline, averting Christmas 2020 shut-downs during warehousing season.
– Learned from Maze & Revil: double-extortion (dark-web leak site—agholeak .onion). Ensure notifications to sector ISACs.

If you are hit, remember:

  1. Collect incident artifacts (PME logs, Kaseya VSA debug … lobby-ids).
  2. Engage law-enforcement before paying (FBI IC3; NCA-uk for EMEA).
  3. Never attempt manual decryption; leverage professional IR firms for key-reuse verification.

Stay safe and immutable!