Modified by: Sabrina Lei Sioting
ALIASES:

Worm:AutoIt/Sohanad.CC (Microsoft); IM-Worm.Win32.Sohanad.qr (Kaspersky); W32/Autorun.worm.f (Mcafee)

 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Propagates via removable drives

The dropped AUTORUN.INF is detected by Trend Micro as Mal_Otorun2.

This worm arrives by connecting affected removable drives to a system.

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It disables Task Manager, Registry Editor, and Folder Options.

It drops copies of itself in removable drives. These dropped copies use the names of the folders located on the said drives for their file names. It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

  TECHNICAL DETAILS

File Size: 1,071,104 bytes
File Type: EXE
File Compression: Aspack
Memory Resident: Yes
Initial Samples Received Date: 04 Feb 2011

Arrival Details

This worm arrives by connecting affected removable drives to a system.

Installation

This worm drops the following copies of itself into the affected system:

  • %Windows%\regsvr.exe
  • %System%\regsvr.exe
  • %System%\svchost .exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows.. %System% is the Windows system folder, which is usually C:\Windows\System32.)

It drops the following files:

  • %System%\setup.ini - contains the same strings as AUTORUN.INF

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It creates the following folders:

  • %system%\28463

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Msn Messsenger = %system%\regsvr.exe

It modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = Explorer.exe regsvr.exe

(Note: The default value data of the said registry entry is Explorer.exe.)

The scheduled task executes the malware every:

  • 9:00 AM everyday

Other System Modifications

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Schedule
AtTaskMaxHours = 0

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Schedule
NextAtJobId = 2

(Note: The default value data of the said registry entry is 1.)

It creates the following registry entry(ies) to disable Task Manager, Registry Tools and Folder Options:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = 0

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = 1

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NofolderOptions = 0

Propagation

This worm drops the following copy(ies) of itself in all removable drives:

  • New Folder .exe

It drops copies of itself in removable drives. These dropped copies use the names of the folders located on the said drives for their file names.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[Autorun]
Open=regsvr.exe
Shellexecute=regsvr.exe
Shell\Open\command=regsvr.exe
Shell=Open

NOTES:
The dropped AUTORUN.INF is detected by Trend Micro as Mal_Otorun2. The created scheduled task is located at %Windows%\Tasks\At1.job.

  SOLUTION

Minimum Scan Engine: 8.900
VSAPI PATTERN File: 7.812.05
VSAPI PATTERN Date: 04 Feb 2011
VSAPI PATTERN Date: 2/4/2011 12:00:00 AM

Step 1

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

Step 2

Identify and terminate files detected as WORM_EMBEDDED.DS

[ 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 3

To enable Registry Editor, Task Manager, and Folder options:

  1. Open Notepad. To do this:
    • For Windows 2000, XP, and Server 2003 users:
      Click Start > Run, type Notepad in the text box provided, then press Enter.
    • For Windows Vista and 7 users:
      Click Start > type Notepad On Error Resume Next
      Set shl = CreateObject(WScript.Shell)
      shl.RegDelete HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System\DisableRegistryTools
      shl.RegDelete HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\System\DisableRegistryTools
      , then press Enter.
  2. Copy and paste the following script:
  3. Save this file as On Error Resume Next
    Set shl = CreateObject(WScript.Shell)
    shl.RegDelete HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System\DisableRegistryTools
    shl.RegDelete HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\System\DisableRegistryTools
     On Error Resume Next
    Set shl = CreateObject(WScript.Shell)
    shl.RegDelete HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System\DisableRegistryTools
    shl.RegDelete HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\System\DisableRegistryTools
    C:RESTORE.VBS.
  4. Click Start>Run again, type C:RESTORE.VBS in the text box provided, then press Enter.
  5. Click Yes at the On Error Resume Next
    Set shl = CreateObject(WScript.Shell)
    shl.RegDelete HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System\DisableRegistryTools
    shl.RegDelete HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\System\DisableRegistryTools
     On Error Resume Next
    Set shl = CreateObject(WScript.Shell)
    shl.RegDelete HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System\DisableRegistryTools
    shl.RegDelete HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\System\DisableRegistryTools
    prompt of the message box to execute the .VBS file.

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\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • NofolderOptions = 0
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Msn Messsenger = %System%\regsvr.exe
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Schedule
    • AtTaskMaxHours = 0

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = Explorer.exe regsvr.exe
      To: Shell = Explorer.exe
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Schedule
    • From: NextAtJobId = 2
      To: NextAtJobId = 1

Step 6

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%\28463

Step 7

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%\setup.ini
%Windows%\Tasks\At1.job

Step 8

Search and delete AUTORUN.INF files created by WORM_EMBEDDED.DS that contain these strings

[ Learn More ]
[Autorun]
Open=regsvr.exe
Shellexecute=regsvr.exe
Shell\Open\command=regsvr.exe
Shell=Open

Step 9

Scan your computer with your Trend Micro product to delete files detected as WORM_EMBEDDED.DS. 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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