In this paper we illustrate security problems coming up with the new concept of the Internet of Things. Passive RFID tags will make up the majority of devices participating in this network. Since passive RFID tags are the devices with the least computing power in the IoT, we focus our investigations on this technology. If we can provide a proper protection for those devices, it will also be possible to use the same security mechanisms on other technologies. In the following section we explain the relevance of passive RFID and security for the upcoming IoT. Later we will provide information about security issues for this technology and explain the current state-of-the-art in research.