The use of radio frequency identification (RFID) technologies in all kinds of wireless network-based applications is becoming truly pervasive. Indeed, applications based on mobile wireless ad hoc networks (MANETs), wireless sensor networks (WSNs), and vehicular ad hoc networks (VANETs), among others, can highly benefit from the adoption of battery-less RFID solutions, such as electronic product code (EPC) tags. However, the use of EPC tags can drastically threaten the security of applications. We present in this chapter an evaluation of threats to the security of EPC tags in wireless network-based applications. We analyze threats to the integrity of the communication between EPC readers and tags due to the use of an insecure wireless channel that does not guarantee the authenticity of the participants. We analyze threats according to a methodology proposed by the European Telecommunications Standards Institute (ETSI). We rank the threats in order of importance. We survey defenses for mitigating high priority threats according to two different research perspectives: hardware-based and algorithmicbased. Hardware-based defenses aim at providing additional security primitives on the RFID devices. Algorithmic-based defenses are software solutions for RFID devices that make use of these new hardware features. We survey current and future trends in each of these categories.