Technology develops very fast today and access to different types of information is much easier than before. An information system is the part of a business system which provides a data picture of the process from a real system. This paper presents ways in which it is possible to protect the information system from the threats it is exposed to on a daily basis. The history of information system development, its roles, tasks and goals are presented in detail. The emphasis is put on the issue of information security. With the use of computers in business practice, the security of information systems and the protection of data and information have become crucial for business functioning. Because of the fact that the operation of the security system can be exposed to various types of threats, necessary precautionary measures have to be taken in order to prevent them. Modern companies are mostly aware of the importance of these measures so they use many of them in order to improve business efficiency and achieve greater competitiveness in the market.