Skulls Trojan on Symbian
Not the first trojan for Symbian phones but one of the first that is out in the wild. From the F-Secure report on the Skulls Trojan
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 you're phone useless and it will prevent it from booting up. 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:
Thanks for the tip Marco