If you have sharing and device detection enabled on your PC, and the phone is connected to the same network (WiFi) then it would be possible to transfer data between the two.
As far as the phone doing it on it's own, I don't see this as very likely. Also, so long as the PC has anti-virus installed, which it should, it shouldn't be any kind of an issue anyways. Should the anti-virus ever detect a threat coming from the phone via the shared network, you should wipe the phone with a factory reset. A quick Google search for "factory reset" with your phones model, should yield plenty of instructionals.