RFID systems are composed by tags (also known as electronic labels) storing an identification sequence which can be wirelessly retrieved by an interrogator, and transmitted to the network through middleware and database information systems. In the case of the EPC Gen2 technology, RFID tags are not provided with on-board batteries. They are passively powered through the radio frequency waves of the interrogators. Tags are also assumed to be of low-cost nature, meaning that they shall be available at a very reduced price (predicted for under 10 US dollar cents in the literature). The passive and low-cost nature of EPC Gen2 tags imposes several challenges in terms of power consumption and integration of defense countermeasures. Like many other pervasive technologies, EPC Gen2 might yield to security and privacy violations if not handled properly. In this chapter, we provide an in-depth presentation of the RFID layer of the EPC Gen2 standard. We also provide security and privacy threats that can affect such a layer, and survey some representative countermeasures that could be used to handle the reported threats. Some of the reported efforts were conducted within the scope of the ARES project