The very idea that someone could "hack" the aircraft systems is so laughably ridiculous I really don't know why I'm bothering, but for the sake of my sanity... this is impossible in the context of the 777. The T7 was introduced into service in 1995, so you can be sure the computer systems on the aircraft date back to technology from the late 80's at BEST. Most of the worlds so-called hackers weren't even BORN then, let alone have any experience working with a system from this era. This is a proprietary architecture, with no open "network ports" or wireless links or anything accessible. Please stop this rubbish. The Teso guy repeatedly mentioned here, did NOT hack an aircraft - he hacked a PC-based ACARS rehost. So he hacked a PC....
On another oft repeated mis-information, R-R did NOT receive any engine data after the ACARS system was deselected. The SATCOM system continued to receive SATCOM pings.... oh, I give up -> READ THIS:
TMF Associates MSS blog » Understanding ?satellite pings??