Posted by Virus Bulletin on Jan 23, 2008
Malware pretends to be media or image file.
A new worm has been sighted in the wild that operates on the Symbian operating system, which is used on many mobile phones. The worm, which researchers at F-Secure have called SymbOS/Beselo, shares many similarities with the SymbOS/Commwarrior worm that was first seen nearly three years ago and affects phones that use the S60 2nd Edition platform, which is used on many Nokia phones. It is believed not to work on 3rd Edition phones.
Infected devices will receive a file that pretends to be either a media file (sex.mp3 or love.rm) or an image file (beauty.jpg). However, unlike Windows, files on Symbian are recognised by their file types rather than by their extension and all three files are in fact .sis application files. When a user tries to open such a file, the malware will attempt to install itself. Users will still have to accept the installation for the worm to become active, but it is known that many will automatically click 'yes'.
Once active, the worm will try to spread itself both by sending itself in MMS messages and by using Bluetooth. Moreover, it will try to spread to generated numbers as well. All these numbers are based in China and belong to the same mobile operator. Some of the numbers have been verified as belonging to real people, rather than being premium numbers. Security researchers are still investigating what the malware tries to achieve this way.
Users are advised to think carefully before clicking 'yes' when asked whether they want to install an application on their phone. Moreover, they should be aware that opening a media or image file does not require the installation of a new application.