We have some isolated reports of users who've been hit by the new Skulls trojan on their phones.
This trojan has been distributed on some Symbian shareware download sites as "Extended Theme Manager" by "Tee-222". If you see it, don't install it on your phone. It will make the smartphone features of your phone useless, so you can still make calls with the phone but that's it, no messages, no web, no applications. Recovery could get tricky, especially if you don't have a third-party file manager software already installed on your phone.
The most obvious symptom of the trojan is that the typical programs on the phone won't work any more, and that their icons get replaced with a a picture of a skull. See below: