This chapter discusses electronic money management via modern payment processing systems. The protocols and architectures of modern payment processing systems are reviewed and the way to identify and eliminate the threats of abuse of an electronic payment system by cyber fraud is discussed. The countermeasures necessary to combat possible depredations are detailed methodically. There is also a brief presentation of the payment processing system of PayPal and the payment gateway service that is provided by VeriSign. While this chapter shows that perceptions of the Web as a dangerous place to operate a business are justified, the main objective is to help e-commerce and online businesses understand the nature of possible threats for the safeguard of their customers’ financial transactions against all risks.