NASA, like any other organization or agency in the world, has a heavy reliance on computer systems. These computers are used for a range of different tasks, including monitoring satellite systems and observing the data they collect.
On the other hand, heavy reliance on computer systems also means that like anything else, NASA is vulnerable to computer hackers. It's also worth noting that NASA has been hacked on numerous occasions.
In some instances, hackers have gone as far as to take full control of some of NASA's satellites. On the other hand, this remote control didn't last very long and NASA didn't find any traces of malice in the anonymous hacker's actions.
The idea that tools being used to observe the world can be readily accessed by hackers who have the desire to take control of them is a scary thought, as many of these satellites have powerful cameras and observation equipment that can invade privacy or blow undercover military operations.
Nevertheless, it also highlights how no computer security is hack-proof. Even top government agencies have trouble keeping the hackers out.