Originally Posted by
areobat
In networking systems, maliciously constructed messages/packets are probably the most common attack vector.
But the ACARS network is more like your home LAN than the Internet; there are few legitimate routes into the system and they're validated as trustworthy before they're allowed to send data. An evil person at an ATC centre could send evil messages, but you pretty much have to trust them regardless of how the messages are transferred.
For this to work, they'd presumably need a suicidal passenger on the aircraft carrying a radio transmitter powerful enough to override the ground transmitters. Which doesn't seem too easy to me.