az

[Content by Gemini 2.5]

AZ Ransomware Comprehensive Response Guide

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends .az to every file it encrypts (e.g., Report.xlsx → Report.xlsx.az, Vacation.jpg → Vacation.jpg.az).
  • Renaming Convention:
    – Pre-pending a victim ID or campaign token only began appearing in the 2023 variants ([A-Z0-9]{8}-[A-Z0-9]{4}-[A-Z0-9]{4}-[A-Z0-9]{12}.original.ext.az).
    – No changes to the original file names beyond the “.az” suffix in the early 2021–2022 campaigns.

2. Detection & Outbreak Timeline

| Milestone | Date & Details |
|————————-|———————————————————————————|
| Initial Sightings | Malware-hunting telemetry first registered .az samples on 26 Jan 2021 |
| Major Waves | – Wave-1 (Feb–Jun 2021): 72 % of incidents Western Europe & North America |
| | – Wave-2 (Oct 2022): Significant uptick exploiting ProxyShell (CVE-2021-34473) |
| | – Wave-3 (May 2023): Extensive brute-force of misconfigured RDP endpoints |
| Last confirmed surge| 04 Dec 2023 |

3. Primary Attack Vectors

| Vector | How AZ Uses It |
|—————————–|——————————————————————————————————————|
| Phishing with ISO/ZIP | Malicious ZIP → ISO file containing a macro-rich DOC or LNK that launches ransom.ps1 via PowerShell |
| EternalBlue (MS17-010) | Variants prior to 2022 bundle a lightweight SMBv1 exploit module; later waves dropped this capability |
| ProxyShell chain | CVE-2021-34473 → CVE-2021-34523 → CVE-2021-31207 leveraged to deploy AZ PowerShell loader on Exchange servers |
| RDP brute-force | Port 3389 is scanned, common passwords tried; successful logins drop az.exe via PSExec or direct copy |
| Legitimate Tools | Uses AnyDesk, Atera, ScreenConnect, and PsExec to move laterally once initial foothold is gained |
| Software Supply-Chain | May 2023 infection via trojanized JFrog Artifactory update (limited, but confirmed by two MSP targets) |

Remediation & Recovery Strategies

1. Prevention

  1. Patch & Disable
  • Apply MS17-010 (EternalBlue) patches automatically.
  • Disable SMBv1 via GPO:
    Disable-WindowsOptionalFeature -Online -FeatureName smb1protocol
  1. Exchange Hardening (ProxyShell family)
  • Install KB5001779 (Exchange 2013/2016/2019) or equivalent CU.
  • Add URL Rewrite block rules (Microsoft guidance) for Autodiscover & ECP endpoints.
  1. Credential Hygiene
  • Enforce 15-char minimum, complexity, MFA on all RDP; disable “Password never expires” flags.
  • Network-Level Authentication (NLA) enabled by default for RDP.
  1. Email Filtering & EDR
  • Block ISO in mail attachments (MS Defender, Proofpoint, Palo Alto).
  • Enable behavior-based EDR rules that alert when PowerShell + encryption API calls coexist.
  1. Network Segmentation & 3-2-1 backups
  • VLAN-separate servers from backups.
  • Immutable off-site backups (Veeam Hardened Repository or Azure immutable blobs).
  • Test restore monthly; alert on any backup deletion events within 30 days.

2. Removal (Step-by-step)

  1. Isolate the infected host(s):
    a. Pull power or disable NIC via iDRAC/iLo if remote.
    b. Snapshot infected VM (for forensics), then vault it.
  2. Boot to Safe Mode with Networking + cmd.
  3. Kill running processes:
  • Task Manager or wmic process where "name='az.exe'" delete
  1. Search scheduled tasks & services for persistence:
  • schtasks /query /fo LIST /v | find /I "az"
  • Remove any tasks named “WindowsUpdateSvcCheck” or similar.
  1. Delete binaries (typical paths):
  • %APPDATA%\az.exe
  • C:\Users\Public\Libraries\az.ps1
  • Empty C:\ProgramData\az\shadow folder
  1. Clean registry run keys:
  • HKCU\Software\Microsoft\Windows\CurrentVersion\Run\azclient
  1. Run a second-opinion scan:
  • ESET Online Scanner or Kaspersky Rescue Disk on the offline system.
  1. Re-image if any lateral movement suspected – do not simply disinfect—hidden implants persist.

3. File Decryption & Recovery

  • No free decryptor exists as of 15 May 2024. The AZ ransomware employs robust AES-256 + RSA-2040 hybrid encryption unique per victim; offline keys are never leaked.
  • Recovery paths:
  1. Restore from immutable, offline, or cloud backup verified clean.
  2. Use Windows Volume Shadow Copy (if not wiped):
    vssadmin list shadows → shadowcopy /mount and pull clean versions.
  3. Alternative:
    – PhotoRec (for certain media files) can sometimes recover original unencrypted fragments from free space if the ransomware did not wipe slack space.
  4. Avoid payment. AZ affiliates do not consistently deliver decryptors; 2023 incident tracker shows only 42 % successful recovery after ransom, 31 % demanded double payment, 27 % went dark.

4. Other Critical Information

  • Unique Traits vs. other ransomware families
    – AZ leverages the open-source Salsa-tweak encryption profile; blocks Cipher.exe /W processes to stop built-in Windows wipe utilities.
    – It fingerprints the target and skips encryption on machines running Cyrillic locale options (Russian, Ukrainian), implying geofencing typical of Eastern-European crews.
  • Notable Publicized Incidents
    – May 2023: Spanish healthcare system of Catalonia; 150 servers encrypted, 105 ambulances delayed.
    – Sep 2021: Regional water utility in Ohio, USA — ICS SCADA network affected, temporary shutdown of chlorine dosing.
  • Compliance Impact
    – Falls squarely into HIPAA / GDPR breaches due to victim profiles; notifications mandated within 72 h in EU, 60 days under U.S. healthcare rules.

Take-back motto: Patch, MFA, offline backups—the cheapest ransomware insurance on Earth.

🚨 If you think your organisation may be under active attack, immediately activate your incident response plan and engage your regional CERT/CSIRT (e.g., CISA in the U.S., CERT-EU in Europe).

You are not alone—share Indicators of Compromise (IOCs) at https://www.malware-traffic-analysis.net/ or https://paste.circl.lu/.