This paper discusses the design and implementation for supporting customized security services in active networks using active networking principles. The customized security services support is based on a secure node architecture that includes an active node operating system security API, an active security guardian, and quality of protection provisions. The support of highly customized security services permits active nodes to satisfy the application-specific dynamic security and protection requirements. It associates quality of protection with network software and application security. Applications can dynamically select the suitable security configurations and services at each active routing node, based on their security and performance requirements. The secure node architecture, together with the support of dynamically customized security services, can provide a fundamental base for securing the active network infrastructure and active applications.