Is "hacking small planes" a separate or larger problem from/than general small-aircraft security? Apparently the DHS has issued a "hacking alert" for small aircraft:


  The alert warns if a hacker gained physical access to certain small planes, they could attach a common device to its wiring. This could provide false flight data including altitude and airspeed, as well as possible access to the autopilot system, potentially leaving a pilot unable to tell whether the reading was accurate and potentially lose control of the aircraft.


This involves physical access to the aircraft, which the FAA said "is unlikely."

Is this particularly different from other attacks not involving "computer hacking" that could be mounted given physical access to an aircraft? For example, is this in some way much less likely to be caught via a pre-flight inspection than any other attack on avionics or other equipment, or much harder to mitigate in flight?

Or is this just more Security Theatre from Homeland Security, raising what's essentially already a known mode of failure (potentially from reasons other than a "hacking attack") for which the aviation community already has procedures in place to mitigate it and continues to monitor and improve these procedures as technology changes over time?
It sounds like just another theoretical scenario.
If that "hacker" wanted to do harm, he could also loosen a few bolts, disrupt the engine timing, plant a bomb, you name it.

Sure, in today's world of aircraft loaded with electronic systems the operators have little knowledge of and trust implicitly, it's quite possible that something that deliberately feeds wrong data to those systems goes unnoticed than disrupting the cylinder timing or mixture control cables would have in the past, but it's still a highly remote possibility.

What it sounds to like me is someone taking the scare of "hackers" breaking into your car and taking over the engine electronics to the next level.