Some of you are missing the point and being a tad facile. The researchers behind the study are on a journey to help the aviation industry develop the next generation of airborne and ground equipment in order to secure aircraft-to-ground and aircraft-to-aircraft communications - something that is completely open to abuse/compromise today.
I attended a session and was given the TCAS hack twice.
The first time, I naturally did what I had to do. But, upon seeing that I was being directed towards the other aircraft, I reacted based on my instincts.
The second time, I reacted opposite to the commands more readily through learned behavior. However, it dawned on me that the first event gave me a lot more time to react compared to the second. The researcher could've easily made it more difficult thus causing a collision, but what would've been the point of that? There is currently nothing in the Airbus and Boeing manuals for such a scenario yet the TCAS "hack" can be done with equipment costing less than a couple of grand.
This is food for thought.