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Discovered: March 22, 2005
Updated: February 13, 2007 12:35:51 PM
Type: Trojan Horse
Systems Affected: EPOC

SymbOS.Drever.B is a Trojan horse that disables certain Symbian OS antivirus programs by overwriting their startup files. The antivirus program affected by this Trojan is SimWorks Anti-Virus for Symbian OS.

It has been reported that the Trojan can be downloaded as a file named Simworks_update.sis. (This Trojan may be located inside a compressed file named The file appears as an update for the Symbian program, SimWorks AntiVirus Software.

Symantec recommends the following to protect against this threat:

    • If Bluetooth is not required, it should be turned off.
    • If you require the use of Bluetooth, ensure that the device's visibility setting is set to "Hidden" so that it can not be scanned by other Bluetooth devices.
    • Avoid use of device pairing. If it must be used, ensure that all paired devices are set to "Unauthorized". This requires each connection request to be authorized by the user.
    • Do not accept unsigned applications (no digital signature) or applications sent from unknown sources. Be absolutely sure of the origin of the application before accepting it.

Antivirus Protection Dates

  • Initial Rapid Release version March 25, 2005
  • Latest Rapid Release version July 17, 2019 revision 021
  • Initial Daily Certified version March 25, 2005
  • Latest Daily Certified version July 18, 2019 revision 002
  • Initial Weekly Certified release date March 25, 2005

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

Technical Description

When SymbOS.Drever.B is executed, it performs the following actions:

  1. Drops the following file:


  1. Overwrites the following files used by the SimWorks AntiVirus application preventing the Simworks Symbian antivirus program from running when the device is started:

    • C:\System\Apps\Antivirus\AntiVirus.lsc
    • C:\System\Apps\Antivirus\Definitions.dat


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.


Removal instructions for hand held devices:

  1. Install a file manager program on the device.

  2. Enable the option to view the files in the system folder.

  3. Delete the following files:

    • Simworks_update.sis

  4. Reinstall your antivirus software.

  5. Exit the file manager.

Writeup By: Robert X Wang