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Worm.AutoIt.OTORUN.AC

June 26, 2019
 Analysis by: John Rey Canon
 ALIASES:

Win32/Packed.Autoit.H (NOD32)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This Worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size:

237,320 bytes

File Type:

Other

Memory Resident:

Yes

Initial Samples Received Date:

20 Jun 2019

Arrival Details

This Worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This Worm drops the following files:

  • %System Root%\MicrosoftSecurity\MicrosoftUpdate.lnk

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)

It drops and executes the following files:

  • %System Root%\MicrosoftSecurity\MicrosoftSecurity.exe

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)

It adds the following processes:

  • %System Root%\MicrosoftSecurity\MicrosoftSecurity.exe /AutoIt3ExecuteScript %System Root%\MicrosoftSecurity\Microsoft.a3x
  • %System%\cmd.exe /c start %System Root%\MicrosoftSecurity/MicrosoftSecurity.exe %System Root%\MicrosoftSecurity/Microsoft.a3x

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It creates the following folders:

  • %System Root%\MicrosoftSecurity\
  • {Drive Letter}:\Microsoft\

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)

Autostart Technique

This Worm adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Microsoft Security = %System Root%\MicrosoftSecurity\MicrosoftCMD.lnk

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Microsoft Security = %System Root%\MicrosoftSecurity\MicrosoftCMD.lnk

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
MicrosoftOffice = %System Root%\MicrosoftSecurity\MicrosoftUpdate.lnk

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Cortana = %System Root%\MicrosoftSecurity\MicrosoftUpdate.lnk

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
HDAudio = %System Root%\MicrosoftSecurity\MicrosoftSecurity.exe /AutoIt3ExecuteScript %System Root%\MicrosoftSecurity\Microsoft.a3x

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
PrintDriver = %System Root%\MicrosoftSecurity\MicrosoftSecurity.exe /AutoIt3ExecuteScript %System Root%\MicrosoftSecurity\Microsoft.a3x

It drops the following file(s) in the Windows Common Startup folder to enable its automatic execution at every system startup:

  • %Common Startup%\Microsoft Security.lnk
  • %Common Startup%\Microsoft Security.lnk
  • %Common Startup%\MicrosoftUpdate.lnk
  • %Common Startup%\MicrosoftUpdate.lnk

(Note: %Common Startup% is the startup folder for all users, which is usually C:\Documents and Settings\All Users\Start Menu\Programs\Startup on Windows 2000, XP, and Server 2003, or C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Other System Modifications

This Worm modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = 0

Other Details

This Worm does the following:

  • It executes the following commands to bypass Windows Firewall:
    • %System%\netsh.exe firewall add allowedprogram "%System Root%\MicrosoftSecurity\MicrosoftSecurity.exe" "MicrosoftSecurity.exe" ENABLE
  • It drops the .lnk files in every infected directory with the following filename:
    • {Infected Directory}\{Parent Folder Name}.lnk
    • {Infected Directory}\My Music.lnk
    • {Infected Directory}\My Pictures.lnk
    • {Infected Directory}\My Reports.lnk
    • {Infected Directory}\Statments.lnk

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.188.04

FIRST VSAPI PATTERN DATE:

21 Jun 2019

VSAPI OPR PATTERN File:

15.189.00

VSAPI OPR PATTERN Date:

22 Jun 2019

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 2

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Microsoft Security = %System Root%\MicrosoftSecurity\MicrosoftCMD.lnk
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Microsoft Security = %System Root%\MicrosoftSecurity\MicrosoftCMD.lnk
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • MicrosoftOffice = %System Root%\MicrosoftSecurity\MicrosoftUpdate.lnk
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Cortana = %System Root%\MicrosoftSecurity\MicrosoftUpdate.lnk
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HDAudio = %System Root%\MicrosoftSecurity\MicrosoftSecurity.exe /AutoIt3ExecuteScript %System Root%\MicrosoftSecurity\Microsoft.a3x
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • PrintDriver = %System Root%\MicrosoftSecurity\MicrosoftSecurity.exe /AutoIt3ExecuteScript %System Root%\MicrosoftSecurity\Microsoft.a3x

Step 5

Restore this modified registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: ShowSuperHidden = 0
      To: ShowSuperHidden = 1

Step 6

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %System Root%\MicrosoftSecurity\Microsoft.a3x
  • %System Root%\MicrosoftSecurity\MicrosoftSecurity.exe
  • %System Root%\MicrosoftSecurity\MicrosoftUpdate.lnk
  • {Drive Letter}:\Microsoft\Microsoft.a3x
  • {Drive Letter}:\Microsoft\MicrosoftSecurity.exe
  • {Drive Letter}:\Microsoft\MicrosoftUpdate.lnk

Step 7

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.  
  • %System Root%\MicrosoftSecurity\
  • {Drive Letter}:\Microsoft\

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Worm.AutoIt.OTORUN.AC. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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