Can anyone answer this query for me? I often leave my bluetooth switched on, on my mobile phone, sometimes i get sent messages to my phone (I dont know who's sending them).

Today at the cinema (in Chiang Mai), i received a bluetooth message 7_7xqeqt.sis, though when i attempt to open it, my phone tells me that "the application is untrusted and may have problems. Install only if you trust provider". So obviously i dont open it.

Does anyone have any idea what would happen if i did open (i.e. could it be a virus, etc)???

Its a virus spread by bloothtooth, normally by a Symbian OS phone like Nokia's series 60 smartphones. Very common in crowded places in Bangkok.

Will drain your battery trying to send itself (in addition to whatever else it does) if you install it.

in your bluetooth settings , set bluetooth as hidden.

if you don't use bluetooth you can just turn it off - will conserve power.

when you do use it , change it to show to all when you pair the 2 BT devices then switch it back to hidden after.