Threat Descriptons



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Aliases :

Skulls.AG, Skulls.AG


Skulls.AG is a malicious SIS file trojan that will replace the system applications with non-functional versions, so that all but the phone functionality will be disabled. If Skulls is installed it will cause all application icons to be replaced with pictures of skulls, and the icons don't refer to the actual applications any more so none of the Phone System applications will be able to start.


A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note: You need administrative rights to change the settings.

Technical Details

Installation to System

Skulls.AG is a SIS file that installs critical System ROM binaries onto the C: drive. The System ROM files are installed with exactly the same names and locations as in the ROM drive.

The Symbian operating system has a feature which causes any file that is in the C: drive to replace the file in the ROM drive with an identical name and location.


Replaces built in applications with non-functional ones and installs Cabir.B and Cabir.I worms, Blankfont.A trojan and Flexispy.A spying application. Flexispy.A is an application that monitors, records, and reports individual phone usage to a third party. The identity of the third party receiving the Flexispy.A data collected is unknown, however the user account number for the spying application is the same as used in Appdisabler.S.

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