There has been discussion in the public about a German consultant finding security issues with the HW NZ 2000 using a desktop computer.
The FAA has stated the described "hack" does not work on certified flight hardware, cannot engage or control the autopilot nor prevent pilots from disengaging the A/P and flying manually.
http://www.businessweek.com/articles/2013-04-12/hacking-an-airplane-with-only-an-android-phone
No one said a hack must be from a smart phone. Hacks are much larger.
Have no idea what happened here, most likely mechanical issue(s), however, I think we all know hacking anything that is computer based, including planes, is very simple for those that choose. Why would they choose to kill 239 innocent people? That is always beyond my understanding, and Malaysia was fine with their monetary failing airlines. No need to harm them. Their government was already exposed, like many larger governments. A plane makes no sense. Malaysia may be controlled, but not on the way to world power. Clearly, news tells us all can take boats to AU, if willing to brave the ocean.