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Discovered: February 20, 2008
Updated: March 28, 2008 6:04:52 PM
Also Known As: W32/Sohana-AX [Sophos], W32/Sohana-AZ [Sophos], W32/Sohana-BA [Sophos], Win32/Spideyit.A [Computer Associates], W32/AutoRun-HA [Sophos], W32/Imaut-F [Sophos], W32/AutoIt-HI [Sophos]
Type: Worm
Infection Length: 807,338 bytes
Systems Affected: Windows

W32.Imaut.CN is a worm that spreads through Yahoo! Instant Messenger and network shares. It may also download potentially malicious code on to the compromised computer.

Antivirus Protection Dates

  • Initial Rapid Release version February 20, 2008 revision 018
  • Latest Rapid Release version July 26, 2019 revision 022
  • Initial Daily Certified version February 20, 2008 revision 024
  • Latest Daily Certified version July 27, 2019 revision 002
  • Initial Weekly Certified release date February 20, 2008

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Technical Description

Once executed, the worm copies itself to the following locations:

  • %System%\regsvr.exe
  • %System%\rundll.exe
  • %System%\winhelp.exe
  • %System%\SCVHOST.exe
  • %Windir%\SCVHOST.exe

It creates and registers the following legitimate DLLs, if they do not already exist:
  • %System%\ijl11pro.dll
  • %System%\COMCTL32.OCX
  • %System%\MSINET.OCX

The worm creates following registry entries, so that it runs every time Windows starts:
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\"Yahoo Messengger" = "%System%\regsvr.exe"
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\"Yahoo Messengger" = "%System%\SCVHOST.exe"
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\"system" = "Winhelp.exe"

The worm also modifies the following registry entries, so that it runs every time Windows starts:
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\"Shell" = "Explorer.exe rundll.exe"
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\"Shell" = "Explorer.exe SCVHOST.exe"

It will attempt to schedule itself to run every day at 09:00 by running the following command:
AT 09:00 /interactive /EVERY:m,t,w,th,f,s,su %System%\winhelp.exe

The above command results in the following file being created:

Next, the worm modifies the following registry entries to execute the schedule command:
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Schedule\"AtTaskMaxHours" = "0"
  • HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Schedule\"NextAtJobId" = "1"
  • HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Schedule\"NextAtJobId" = "2"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Schedule\"NextAtJobId" = "1"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Schedule\"NextAtJobId" = "2"

The worm then modifies the following registry keys to hide its presence on the compromised computer:
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\"NofolderOptions" = "0"
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System\"DisableTaskMgr" = "0"
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System\"DisableRegistryTools" = "1"

The worm checks the following subkey for any shared network folders:

It then copies itself to those folders as well as any mapped drives that it finds, excluding A:, as the following files:
  • %DriveLetter%\New Folder.exe
  • %DriveLetter%\regsvr.exe

The worm also creates the autorun.inf file in the same location so that it runs when the drive is accessed.

After having copied itself to the network share, the worm may create the following registry entry so that it appears as a shared folder:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\WorkgroupCrawler\Shares\"Shared" = "\New Folder.exe"

The worm then attempts to download configuration/update information from the following URL's
  • [http://]crackspider.net/setti[REMOVED]
  • [http://]crackspider.net/setti[REMOVED]
  • [http://]nhattruongquang.0catch.com/setti[REMOVED]

It may then create the files below to store this downloaded configuration information:
  • %System%\settings.ini
  • %System%\setup.ini
  • %Windir%\winhelp.ini

Note: The downloaded configuration information includes URLs of additional malicious content.

The worm attempts to close any windows with the following strings in the title:
  • Bkav2006
  • Registry
  • System Configuration
  • Windows mask

It deletes the following registry value:

It also checks for and closes any window with the title FireLion.

It then deletes the following registry value and restarts the compromised computer:

In addition, the worm will periodically end any processes containing the following strings:
  • game_y.exe
  • cmder.exe

The worm attempts to send one of the following messages to random contacts in the user's Yahoo! Instant Messenger contact list:
  • Happy sankranti/pongal [http://]crackspider.net[REMOVED]
  • [http://]vao day coi co con nho nay ngon lam http://nhattruongquang.0catch.com[REMOVED]
  • [http://] nghe bai nay di ban http://nhattruongquang.0catch.com[REMOVED]
  • [http://] nghe bai nay di ban http://nhattruongquang.0catch.com[REMOVED]
  • [http://]n gi chua, vao day coi di http://nhattruongquang.0catch.com[REMOVED]
  • [http://]eb nay coi cung hay, vao coi thu di http://nhattruongquang.0catch.com[REMOVED]
  • [http://]lang thang lan trong bong toi buot gia, ve dau khi da mat em roi[REMOVED]
  • [http://]oi dung noi se yeu minh toi mai thoi thi gio day toi se vui hon. Gio nguoi lac loi buoc chan ve noi xa xoi, cay dang chi rieng minh toi... http://nhattruongquang.0catch.com[REMOVED]
  • [http://] em niem vui khi duoc gan ben em, tra lai em loi yeu thuong em dem, tra lai em niem tin thang nam qua ta dap xay. Gio day chi la nhung ky niem buon... http://nhattruongquang.0catch.com[REMOVED]

Note: The URL in the IM message is determined by the configuration file downloaded by the worm, otherwise, the URL in the link will default to the above link if the configuration file is unavailable.


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.


You may have arrived at this page either because you have been alerted by your Symantec product about this risk, or you are concerned that your computer has been affected by this risk.

Before proceeding further we recommend that you run a full system scan . If that does not resolve the problem you can try one of the options available below.

If you are a Norton product user, we recommend you try the following resources to remove this risk.

Removal Tool

If you have an infected Windows system file, you may need to replace them using from the Windows installation CD .

How to reduce the risk of infection
The following resources provide further information and best practices to help reduce the risk of infection.

If you are a Symantec business product user, we recommend you try the following resources to remove this risk.

Identifying and submitting suspect files
Submitting suspicious files to Symantec allows us to ensure that our protection capabilities keep up with the ever-changing threat landscape. Submitted files are analyzed by Symantec Security Response and, where necessary, updated definitions are immediately distributed through LiveUpdate™ to all Symantec end points. This ensures that other computers nearby are protected from attack. The following resources may help in identifying suspicious files for submission to Symantec.

Removal Tool

If you have an infected Windows system file, you may need to replace them using from the Windows installation CD .

How to reduce the risk of infection
The following resource provides further information and best practices to help reduce the risk of infection.
Protecting your business network

The following instructions pertain to all current Symantec antivirus products.

1. Performing a full system scan
How to run a full system scan using your Symantec product

2. Restoring settings in the registry
Many risks make modifications to the registry, which could impact the functionality or performance of the compromised computer. While many of these modifications can be restored through various Windows components, it may be necessary to edit the registry. See in the Technical Details of this writeup for information about which registry keys were created or modified. Delete registry subkeys and entries created by the risk and return all modified registry entries to their previous values.

Writeup By: Sean Kiernan