Broken Encapsulation, how hacking is really just finding ways to play middle man to component systems.
The annual black hat and defcon conferences are well known events where hackers and crackers of all types of systems come together to demonstrate their latest "exploits". These range from ways to snoop data or voice off of open cell or wifi networks to ways to modify the function of various hardware systems. In this years Defcon conference a team of hackers introduced some exploits of the computer systems inside a modern automobile. You can see a video of some of their results here , the interesting thing about hacking though that goes beyond the FUD generation that the media seems intent on producing by publishing such stories is that they aren't really that surprising. Engineering systems is about learning to cleverly use abstractions and functional encapsulation to built extremely complex systems. In object oriented programming the concepts of encapsulation are a fundamental aspect of good OO design principles and I've written extensively on these ideas in posts i