SymbOS.Commdropper.A

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Discovered: May 17, 2006
Updated: February 13, 2007 12:55:34 PM
Type: Trojan Horse
Systems Affected: Symbian OS



SymbOS.Commdropper.A is a Trojan horse that affects Symbian series 60 phones. The Trojan drops SymbOS.Commwarrior.F onto the compromised device.

Antivirus Protection Dates

  • Initial Rapid Release version May 17, 2006
  • Latest Rapid Release version August 20, 2008 revision 017
  • Initial Daily Certified version May 17, 2006
  • Latest Daily Certified version August 20, 2008 revision 016
  • Initial Weekly Certified release date May 17, 2006

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


Technical Description


It has been reported that the Trojan arrives as the following file:
Update TomTom Mobile 5.40.sis

When a user opens this file, the phone installer will display a dialog to warn users that the application may be coming from an untrusted source and may cause potential problems. If the user clicks yes, the device will display the following message prompting the user to install the threat:

Install
Update TomTom Mobile 5.40

When SymbOS.Commdropper.A is executed, it performs the following actions:

  1. May display the following message when installed:

    In order to update the application of its movable device, memory card recorder must have lector/una. Microsoft ActiveSync?, Sony Ericsson PC suite or Nokia PC cannot be used Suite to install this update. We recommended to him encarecidamente that it makes a backup of its memory card of TomTom MOBILE before installing the new application. The following passages of update of the application include a passage for the accomplishment of a backup. No of the following steps skips.

    Cracked & Updated by [REMOVED]. (The life is a way. You do not
    lose yourself. )

  2. Drops the following files:

    • [DRIVE LETTER]\system\apps\TTMOBILE\CurrentMap.dat
    • [DRIVE LETTER]\system\apps\TTMOBILE\Game.cfg
    • [DRIVE LETTER]\system\apps\TTMOBILE\TREMOR.dll
    • [DRIVE LETTER]\system\apps\TTMOBILE\TTMOBILE.APP
    • [DRIVE LETTER]\system\apps\TTMOBILE\TTMOBILE.APP_org
    • [DRIVE LETTER]\system\apps\TTMOBILE\TTMOBILE.RSC
    • [DRIVE LETTER]\system\apps\TTMOBILE\TTMOBILE.aif
    • [DRIVE LETTER]\system\apps\TTMOBILE\TTMOBILE.mbm
    • [DRIVE LETTER]\system\apps\TTNCONTACTS\RecQWRD.mdl
    • [DRIVE LETTER]\system\apps\TTNCONTACTS\TTNCONTACTS.exe (A copy of SymbOS.Commwarrior.F.)

      Note:
    • The [DRIVE LETTER] variable refers to the drive letter that is used to represent the device itself or the memory card. The actual value will depend on the choice the user makes during the installation process.
    • The following file is also created by the device Installer, not the Trojan itself:

      [DRIVE LETTER]\system\install\Update TomTom Mobile 5.40.sis


Recommendations

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


  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:

    • [DRIVE LETTER]\system\apps\TTMOBILE\CurrentMap.dat
    • [DRIVE LETTER]\system\apps\TTMOBILE\Game.cfg
    • [DRIVE LETTER]\system\apps\TTMOBILE\TREMOR.dll
    • [DRIVE LETTER]\system\apps\TTMOBILE\TTMOBILE.APP
    • [DRIVE LETTER]\system\apps\TTMOBILE\TTMOBILE.APP_org
    • [DRIVE LETTER]\system\apps\TTMOBILE\TTMOBILE.RSC
    • [DRIVE LETTER]\system\apps\TTMOBILE\TTMOBILE.aif
    • [DRIVE LETTER]\system\apps\TTMOBILE\TTMOBILE.mbm
    • [DRIVE LETTER]\system\apps\TTNCONTACTS\RecQWRD.mdl
    • [DRIVE LETTER]\system\apps\TTNCONTACTS\TTNCONTACTS.exe

  4. Exit the file manager.


Writeup By: Yana Liu