In the information society, cyber attacks launched upon the information technology infrastructure are increasingly diversified and complex. Cybercriminals or black hat hackers use a wide range of techniques, tactics and procedures to compromise computer systems. APT and ransomware attacks are two cyber security threats that many companies and government institutions face. Ransomware is a medium complexity attack, while APT is a high complexity cyber attack. The emergence of certain hybrid malicious programs (computer worm-ransomware) and the diversification of attack vectors represent new challenges for specialists and organizations.