The focus of this paper is set on the activities of the e-commerce and computer crime. Also, the main objective is to explain the impact that computer crime has on electronic commerce and its users. The first part of the paper reflects on the development of information and communication technologies and the distribution of computer networks and all of the wider use of the Internet, which affects the development of the society according to the global information society. Furthermore, the development of e-commerce and the benefits that it brings to today's business is presented and it is defined as the economic activity of buying and selling products and services, that takes place online, without paper documents. After that, the concept of cyber-crime was explained in more detail, which represents any violation of criminal law which includes knowledge of computer technology for its perpetration, investigation or criminal prosecution. In the second part of the paper threats of security of e-commerce are analyzed, as well as the very purpose of that security which is described as asset protection of e-commerce from unauthorized access, use, alteration or destruction. Most widespread threats to the safety of e-commerce are identity theft, spoofing and pharming attacks, destroying or altering the pages of e-commerce and so on and so forth. Based on the examples from practice, the effects that different types of cyber-crime have on today's most famous online trading platform are shown. At the very end of the paper, previously collected information are discussed and conclusions are drawn about the research topic.