This bachelor thesis focuses on the issue of an unsolicited mail, also known as a spam. Mo-reover, the thesis deals with preventive measures against these spams on the side of banking institutions operating in the Czech Republic.The objective of the theoretical part is to famili-arise a reader with basic characteristics of spam, its development, possible methods of its prevention and risks, which are related to the banking sector. In practical part of the thesis, a reader can find selected banking sectors operating on the Czech market. Those were analysed in the terms of providing adequate and good-quality information about the spam, its possible security risks and the security features of the internet banking. The outcome of the analysis i...