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WORM_SOHAND.SM
Aliases: Worm:Win32/Tupym.A (Microsoft), Worm.Win32.AutoRun.fnc (Kaspersky), Win32/Autoit.EB (Eset), W32/AutoRun-BUC (Sophos), W32.Imaut (Symantec)
Malware type: Worm
Destructive: No
Platform: Windows 2000, Windows XP, Windows Server 2003, Windows Vista, Windows 7
Encrypted: No
In the wild: Yes

Overview


Infection Channel: Propagates via removable drives, Downloaded from the Internet, Dropped by other malware, Propagates via instant messaging applications

This worm arrives by connecting affected removable drives to a system. It arrives by accessing affected shared networks. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy. It uses the default Windows folder icon to trick users into opening the file. Double-clicking the file executes this malware.

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: 836,165 bytes
File type: EXE
Memory resident: Yes
Initial samples received date: 29 May 2010
Payload: Downloads files, Terminates processes

Arrival Details

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

It arrives by accessing affected shared networks.

It 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 copies of itself into the affected system:

  • {install directory}\system3_.exe

It drops the following component file(s):

  • {install directory}\autorun.ini - copy of autorun.inf

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

It uses the default Windows folder icon to trick users into opening the file. Double-clicking the file executes this malware.

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
Yahoo Messengger = {install directory}\system3_.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 system3_.exe"

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

The scheduled task executes the malware every:

  • 9:00 AM

Other System Modifications

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
WorkgroupCrawler\Shares
shared = "\New Folder.exe"

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

It modifies the following registry key(s)/entry(ies) as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Start Page = "http://www.{BLOCKED}mworld.50webs.com "

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Default_Page_URL = "http://www.{BLOCKED}mworld.50webs.com "

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Default_Search_URL = "http://www.{BLOCKED}mworld.50webs.com "

(Note: The default value data of the said registry entry is {default search page}.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Search Page = "http://www.{BLOCKED}mworld.50webs.com "

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Start Page = "http://www.{BLOCKED}mworld.50webs.com "

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

Propagation

This worm searches for folders in all physical and removable drives then drops copies of itself inside the folder as {folder name}.EXE.

It drops the following copy of itself in all physical and removable drives:

  • New Folder.exe

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=system3_.exe
Shellexecute=system3_.exe
Shell\Open\command=system3_.exe
Shell=Open

It sends messages that contain links to sites hosting remote copies of itself using the following instant-messaging (IM) applications:

  • Yahoo Messenger
  • Google Talk

Process Termination

This worm terminates the following processes if found running in the affected system's memory:

  • game_y.exe
  • cmd.exe

Download Routine

This worm connects to the following URL(s) to download its configuration file:

  • http://{BLOCKED}ay.com/asdb{1-50}/setting.ini
  • http://{BLOCKED}u{1-25}.0catch.com/set/setting.ini

It saves the files it downloads using the following names:

  • {install directory}\setting.ini

NOTES:

Upon execution, the malware checks the OS version of the affected machine. If it is Windows Vista, it sets the {install directory} to C:\Desktop or %User Temp%.

If the worm is not running on Windows Vista, the {install directory}is set to %System% or %Windows%.

This worm enumerates shared drives by checking the value from following registry:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\WorkgroupCrawler\Shares

It then copies itself to the shared drive as New Folder.exe. It also copies its corresponding AUTORUN.INF to automatically execute the worm.

It terminates processes of applications with the following Window Names:

  • [FireLion]
  • Bkav2006
  • Registry
  • System Configuration
  • Windows Task

Solution


Minimum scan engine: 9.200
First VSAPI Pattern File: 7.206.12
First VSAPI Pattern Release Date: 29 May 2010
VSAPI OPR Pattern Version: 7.207.00
VSAPI OPR Pattern Release Date: 30 May 2010

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_SOHAND.SM

[ 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

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\Run
    • Yahoo Messengger = "C:\WINDOWS\system32\system3_.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\WorkgroupCrawler\Shares
    • shared = "\New Folder.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Schedule
    • AtTaskMaxHours = "0"

Step 4

Restore these modified registry values

[ Learn more ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.


  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = "Explorer.exe system3_.exe"
      To: Shell = "Explorer.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • From: Start Page = "http://www.{BLOCKED}mworld.50webs.com"
      To: Start Page = {default}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
    • From: Default_Page_URL = "http://www.{BLOCKED}mworld.50webs.com"
      To: Default_Page_URL = {default}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
    • From: Default_Search_URL = "http://www.{BLOCKED}mworld.50webs.com"
      To: Default_Search_URL = {default search page}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
    • From: Search Page = "http://www.{BLOCKED}mworld.50webs.com"
      To: Search Page = {default}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
    • From: Start Page = "http://www.{BLOCKED}mworld.50webs.com "
      To: Start Page = {default}

Step 5

Search and delete these components

[ Learn more ]
There may be some components 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.
{install directory}\autorun.ini

Step 6

To delete the added job file:

  1. Click on Start>Programs>Accessories>System Tools>Scheduled Tasks
  2. Double-click on a job file.
  3. Check if the malware path and file name is in the Run: box.
  4. If it does, delete the job file.
  5. Repeat step 2-4 for the remaining job files.

Step 7

Search and delete AUTORUN.INF files created by WORM_SOHAND.SM that contain these strings

[ Learn more ]
  • [Autorun]
  • Open=system3_.exe
  • Shellexecute=system3_.exe
  • Shell\Open\command=system3_.exe
  • Shell=Open

Step 8

Scan your computer with your Trend Micro product to delete files detected as WORM_SOHAND.SM. 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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Analysis By: Automation
Modified By: Sabrina Lei Sioting

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