Well, let's start by making a complete sentence of your passive voice example (it isn't a sentence):
I'm not worried about my phone being tapped.
To put it in active voice, you have to include the tapper of the phone:
I'm not worried about anyone (or someone) tapping my phone.
The point is that in the passive voice the phone is being tapped (or not) by someone, and that's understood. As a general rule, if you want to change the passive to the active, you take the by clause and make it the subject of the sentence. If there isn't a by clause, you need to imagine one. (Who is tapping the phone? Someone.)
Now, in the active voice, anyone and someone are pretty much interchangeable. However, in the passive voice, anyone is rather more emphatic than someone. Anyone has the sense of I'm quite sure that nobody is tapping my phone, where someone has the sense of I don't think that there's a person out there who is tapping my phone. If you just say I'm not worried about my phone being tapped, the generally understood meaning is by someone. You would add by anyone for emphasis, and stress the word itself as well.