Reported by F-Secure the Skulls Trojan places corrupted version of Symbian OS component on a devices "C" drive and replaces program icons with Skulls icons. The corrupted Symbian OS components mean that the normal function of the device is corrupted and application rendered unrunnable.

As with previous malware for Symbian OS Skulls relies on user ignorance more than any real vulnerability in Symbian OS to attack Series 60 devices. Users have to ignore the installation warnings to be affected by the program. Ultimately it underlines the benefits of the Symbian Signed program and the need for any user to take care with the programs they load on their device when the program is not signed.

F-Secure Description: The Skulls SIS file is named "Extended theme.SIS", it claims to be theme manager for Nokia 7610 smart phone, written by "Tee-222".

If Skulls is installed it will cause all application icons to be replaced with picture of skull and cross bones, and the icons don't refer to the actual applications any more so none of the Phone System applications will be able to start.

This basically means that if Skulls is installed only the calling from the phone and answering calls works. All functions which need some system application, such as SMS and MMS messaging, web browsing and camera no longer function.

If you have installed Skulls, the most important thing is not to reboot the phone and follow the disinfection instruction in this description.