The Zeroconf protocols enable IP-based devices to communicate without any prior configuration or infrastructure services such as Domain Name Service (DNS) or Dynamic Host Configuration Protocol (DHCP). Ensuring that these protocols work securely is a challenging task. In this section, we focus on the security aspects of the Zeroconf technology. We discuss some potential security threats and present an analysis of two possible solutions that can be used to secure Zeroconf networks. Finally, we discuss the results obtained by implementing security in a real Zeroconf network, and its impact on the performance of Mono.Zeroconf, in the Windows XP environment.