Nowadays hacker attacks on computers or smartphones of everyday users have become commonplace. Unfortunately, increasing number of sophisticated attacks are being targeted against critical infrastructure or banking systems. The threat from hackers is very serious. As a result, institutions exposed to the attacks are obliged to take action to repulse them, because the consequences of intrusions into internal systems can be far-reaching. Numerous cases of effective hacker activities are not rare, as shown by cases from recent years.