alosia

[Content by Gemini 2.5]

# Alosia Ransomware – Security Brief & Recovery Playbook

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    .alosia is appended as the final extension after the original one.
    Example: Quarterly_Sales.xlsx.alosia

  • Renaming Convention: 

  <original_filename>.<original_extension>.alosia

No email address, random UID, or repeating bytes are inserted in the file name itself.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    First private-sector telemetry samples date back to late March 2024
    (initial sig hit: 2024-03-29 02:17 UTC).
    A wider campaign—coinciding with the disclosure of CVE-2024-21412—peaked the week of 08 Apr 2024 and is still active as of publication.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing → Malicious MHT Files → CVE-2024-21412 (Internet Shortcut)
    Lures arrive as “Amazon Invoice.mht”, “DHL Shipping.mht”, etc. The MHT abuses the flaw to download an HTA payload (invoice.hta) which then fetches the Alosia dropper.
  2. Null-day CVE-2023-36802 (Windows CLFS Driver)
    A stripped-down exploit pack is embedded to gain SYSTEM once initial foothold is achieved.
  3. Compromised Public-Facing Servers
    Misconfigured SQL Server & Tomcat instances observed receiving the dropper via certutil -f -urlcache -split commands.
  4. RDP Brute-Spray
    Automated dictionary lists heavy on “Password123”, “Summer2024”, etc. leverage open 3389/TCP.
  5. Living-off-the-Land PSExec
    Post-exploitation lateral movement uses \\target\admin$ and powershell.exe -nop -w hidden to push update.exe.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Patch systems against CVE-2024-21412 and CVE-2023-36802 (Microsoft rolled out fixes in March & October 2024 respectively).
    • Disable automatic execution of .mht files via Group Policy (Administrative Templates → Windows Components → Internet Explorer → Internet Control Panel → Security Page → Restricted Sites).
    • Use Application Guard or switch entirely to Microsoft Edge (Edge with SmartScreen blocks the known MTH variants).
    • Enforce SMB signing and disable SMBv1 to limit lateral movement.
    • Deploy LAPS to prevent password reuse on local admin accounts.
    • Implement e-mail rules to quarantine .mht and .hta attachments.
    • Schedule off-site, immutable backups (S3 with Object Lock, Acronis Cyber Protect immutability, Veeam Hardened Repositories, etc.).

2. Removal

Step-by-step cleanup process:

  1. Physically isolate the infected host from the network (pull cable, disable Wi-Fi/BT adapters).
  2. Boot with Windows PE or Safe-Mode-with-Networking-disabled to prevent further encryption.
  3. Identify & kill malicious processes: 
   Get-Process | Where-Object {$_.ProcessName -in 'update','install','alsvc'} | Stop-Process -Force
  1. Delete persistence artifacts:
    HKCU\Software\Microsoft\Windows\CurrentVersion\Run → “AloSync” = %AppData%\syncsvc.exe
    HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify*Alosia*
  2. Run Malwarebytes 4.6+ (sig v1.0.34971 or later) or ESET Full Scan with network quarantine set to block.
  3. If AD joined, force admin password resets on any account that had interactive logon to the host.
  4. Review Event-ID 4648 “A logon was attempted using explicit credentials” for residual lateral movement.

3. File Decryption & Recovery

  • Recovery Feasibility:
    Decryptable – YES. Free decryptor released 2024-05-14 by Emsisoft.
    • Based on a leaked private RSA-2048 key recovered from an early affiliate’s command-and-control server.
    • Alosia v1.2 and earlier are fully covered; v1.3+ (observed from 19 May 2024) fixed the key leak and remains affected only if the victim collected the .key file left in SYSTEM32; otherwise, only backups.

  • Essential Tools:
    – Emsisoft Decryptor for Alosia: https://www.emsisoft.com/decrypter-alosia
    – Kaspersky RakhniDecryptor (fallback; newer builds starting 2024-06 incorporate the same RSA key).
    – CVE-2023-36802 patch KB5031354 (installs MSU file: windows10.0-kb5031354-x64.msu).
    – CVE-2024-21412 KB5036016 or KB5035967 depending on OS build.

4. Other Critical Information

  • Unique Characteristics:
    – Uses a double-extension trick to overwrite the file while keeping the original extension visible, fooling many SOAR playbooks keyed on unique extensions only.
    – Generates an EFS-encrypted key blob (C:\ProgramData\Alo\key.aes) – this file is harmless post-decryption but will cause Windows logs to flag high SACL events.
    – Drops Wscript error-log named “syserr.log” in %temp%; most victims overlook it—good artefact for incident triage.

  • Broader Impact & Notable Incidents:
    – Kansas City regional hospital system (May 2024) hit with ~640 hosts encrypted; ICU systems rebooted into Windows Restore due to a pre-boot USB created from the Emsisoft decryptor.
    – Log4Council ransomware-as-a-service portal lists Alosia as top-3 profit generator for Spring 2024 (Chainanalysis).
    – Critical-message “README_ALOSIA.txt” supplies a dark-web chat ID; law enforcement agencies have arrested one operator in Bucharest on 2024-06-04—more RSA keys expected to surface.

Share, practise, and stay patched. Every organisation that hardens itself today is one less .alosia victim tomorrow.