It is acommonplace that the internet is one of the most powerful tools at the disposal of contemporary societies; it is also one of the most dynamically developing ways of information transfer. Access to information is the most important and desirable aim of human aspirations. The internet is still developing very dynamically, thus defying any efforts at determining the limits of its advancement; it creates infinite opportunities in various areas, while its great potential affects all aspects of human existence. For years the internet has also been the medium for financial transactions involving electronically regulated cash flow. Many of these transactions are carried out with the use of payment cards, which for many people constitute anobvious alternative to traditional transactions involving cash. The history of payment cards elsewhere in the world goes back to the beginning of the previous century, but in Poland they came into use much later, i.e. in the mid-1990s. The development of the internet, and especially the speed of data transfer which it offers, have greatly facilitated the transactions involving payment cards. This fact poses aquestion concerning the security of such transactions. The popular and universal character of online payments, not necessarily with the use of payment cards, resulted in the emergence of crime involving identity theft and conducting illegal transactions.