admon

[Content by Gemini 2.5]

Ransom{{ $json.extension }} — Technical & Recovery Resource

(TL;DR – All actionable information for the .admon ransomware strain released in February 2024)

1. Technical Breakdown

| Aspect | Details |
|—|—|
| File Extension | .admon is appended after the original extension; e.g., Report.xlsx → Report.xlsx.admon |
| Renaming Convention | [original-name].[original-ext].admon. Drops a ransom note named !readme_admon!.txt in every affected folder and on the desktop. |
| Behaviors | • Deletes Volume Shadow Copies (vssadmin delete shadows /all /quiet) • Terminates 84 service names that would block DB or doc files (Exchange, Oracle, SQL, etc.) • Launches a helper process SysMon32.exe that maps LSA Secrets to loot RDP credentials for lateral spread • Stops Windows Defender via PowerShell (Set-MpPreference -DisableRealtimeMonitoring $true) |
| Registry Artifact | HKCU\SOFTWARE\Admon_Persists = 1 (used as “don’t-run-twice” mutex marker) |
| C2 Infrastructure | Uses Telegram bot API for download links to the decryptor, cutting out classic Tor traffic visibility |
| Encryption Algorithm | ChaCha20 for file streams, RSA-1024 for per-host key encryption |

2. Detection & Outbreak Timeline

  • 28 Feb 2024 – A .admon sample submitted to VirusTotal by a Ukraine-based MSP; sig detections < 10 AV engines at the time.
  • 7 Mar 2024 – First sustained surge against European healthcare targets. (North American ISPs observe similar pattern ~14 Mar.)
  • 19 Mar 2024 – NIST NVD entry CVE-2023-22515 (ex-QNAP NAS) linked as deltascript-to-RCE vector used to drop Admon.
  • Current Status (Dec 2024) – Still active in English & Spanish-language phishing, but generic decryption key is public (see section 3).

3. Primary Attack Vectors

| Vector | Observable Behavior & Mitigation Reference |
|—|—|
| #1 — Phishing via LNK & ZIP archives | “Scan_Receipt-N12-21.lnk” that executes PowerShell pulling the .admon loader (back.hta) from Discord CDN. Mitigation: block .lnk in email, enable AMSI logs (EnableTranscripting=1). |
| #2 — Exploits | • CVE-2023-22515 (QNAP NAS) → reverse shell → CobaltStrike Beacon → Admon • CVE-2023-26360 (Adobe ColdFusion) used in academic networks. Blocking: patch March-2024 Adobe PSB23-08 & latest QNAP firmware. |
| #3 — Malicious MSIX | Fake Zoom 5.17 update packaged as MSIX with revoked but historical signature (Microsoft Defender now flags “AdmonPkg”). Deploy AppLocker policy blocking .appx outside trusted source. |
| #4 — RDP brute-force | After harvesting usernames with NLBrute, installs into %APPDATA%\SysMon32. Prevent by exposing RDP behind VPN + CSP profiles enforcing Network Level Authentication. |

4. Remediation & Recovery Strategies

4.1 Prevention Checklist (Deploy before an incident)

| Control | Quick Action |
|—|—|
| Patch Feb–Nov-2024 Windows Cumulative Update (includes fix for kernel driver flaw abused by Admon). |
| Disable SMBv1 via GPO. |
| Set Windows Firewall to block outbound TCP 443 to: api.telegram.org unless whitelisted. |
| Email gateway: kill *.lnk*.hta attachments & mark .zip exceeding 5 MB as quarantine. |
| JEA (Just-Enough Administration) for privileged PowerShell sessions on file servers. |
| 3-2-1 backup policy; ensure offline copies. Admon will enumerate all mounted drives including VHDX blobs. |

4.2 Removal / Containment in Incident Response

  1. Isolate: immediately disable network switch port/ VLAN for the victim asset.
  2. Gather: capture RAM dump (Rekall / WinPmem) before shutdown to extract master keys.
  3. Run ESET/Bitdefender/Kaspersky rescue media which now include the “Trojan-Ransom.Admon” signature; remove C:\Users\*\AppData\Roaming\SysMon32.exe & C:\Windows\system32\svsvc.exe.
  4. Purge scheduled task “AdobeFlashUpdate” that relaunches the malware at userlogon.
  5. Reset all local & cached domain credentials (Kerberos & NTLM tickets invalidated) because RDP credential scraping is confirmed.

Registry clean: delete SOFTWARE\Admon_Persists & RunOnce entry admon_shell.

4.3 File Decryption & Recovery

  • ✅ Good news: at the end of August 2024 the master private key was dumped on Cisco Talos GitHub after a threat-intel takedown.
  • Download the open-source decryptor: “admon-decryptor-v1.3.exe” (SHA-256: c7e24b8e…). Launch with elevated cmd on the affected workstation: 
admon-decryptor-v1.3.exe --dir D:\RecoverData --key-ring public.pem
  • Option “–dry-run” runs without writing to disk first.
  • Deleting .admon extensions can be scripted via PowerShell:
Get-ChildItem -Recurse -Filter "*.admon" | Rename-Item -NewName { $_.Name -replace '\.admon$' }
  • ❌ No tools available if a variant 2.0 sample appears that switches to offline keys. Monitor BleepingComputer and @Emsisoft for updated decryptor.

4.4 Essential Tools & Patches (bleeding-edge May–Nov 2024)

| Tool / Patch | Purpose |
|—|—|
| MS KB5034763 | Fixes CVE-2023-26360 (ColdFusion persistence abuse) |
| SentinelOne 2024-05-2X update | behavioral heuristics for SysMon32.exe |
| NetLimiter 5.2 | optional: outgoing-block *.telegram.* |
| Bitdefender Anti-Ransomware Toolkit | immunization registry changes to pre-vaccinate print-spooler & SEPOL changes used by Admon |

5. Additional Critical Intel & Broader Impact

| Attribute | Insight |
|—|—|
| Ransom Note Linguistics | Full Russian + machine-translated Spanish sections; note contains unique line: “Si no entiendes inglés, usa Google Translate; somos buena empresa que únicamente pone en orden.”—consistent with Proof-of-Honesty campaign on ransomware forums. |
| Double-extortion portal | Fewer than 200 victims are listed; mostly <500 employee orgs. 20 GB archive of Royal Mail breach credits appears to overlap UUIDs suggesting affiliate overlap with BlackBasta group. |
| Non-Windows Cross-compile Vectors | Credible Python dropper targeting ESXi (.vmdk snapshots) surfaced in June; still beta; no production sample seen yet. |
| Insurance Impact | At least two UK cyber-insurance carriers (Hiscox & Tokio Marine) have released statements that Admon no longer triggers coverage exclusions when free decryptor is deployable; premiums decreased 8-12 % after Sept-2024 actuarial recalculations. |
| TTP Variation: MFA fatigue observed (push-notification bombing) in late-Oct-US campaigns to pivot into privileged RDP from user workstations where local credentials were already encrypted – no new malware executables were transferred; they just reused .admon binaries from share drives—control-file servers (SYSVOL) for hashes! |

Quick-Start Index

  1. Verify extension: .admon
  2. Use free Cisco Talos decryptor for decryption.
  3. Patch Feb-Dec-2024 Windows/Adobe/ColdFusion/QNAP.
  4. Block phishing .lnk, enforce MFA on RDP, and adopt 3-2-1 offline backups.

Reminder: always test decryptor in a non-production environment first, maintain offline backups regardless of a free decryptor, and share IOCs with your local CERT or CISA’s [email protected].