Alongside with huge advantages, computers bring challenges. And almost all of these challenges are connected with the possibility to interfere with the operation of your computer from the outside. Fighting hackers has become a "pain in the neck" for many people, and the word "virus" is often associated with a computer rather than medicine. The failure to fight hackers makes us look for the reasons not in the software as it is done today, but in something more deep. Computers are designed to run programs - various algorithms written in programming languages. The word “various” means almost “all” here. The computer runs any program. Predefined functions can be performed not only by computers - for example, finite-state machines can perform them too. The difference is that the computer executes "any" program. The computer is incomparably more flexible and versatile compared to the finite-state machine.