Ian from Forogotten Weapons and Karl went to Defcon and heard about how the two hackers were able to hack in to TrackingPoint. In short, it required actual physical posession of the system and uploading software.
https://www.full30.com/video/9d56a035b6771c5498798613066505ec
https://www.full30.com/video/e74a10ccc12a118e4e8751c99f0d6cef
Edit: Forgotten member added.