Due to end-to-end design principle in distributed applications, many emerging security problems could not be solved by conventional security technologies, such as firewalls and IDSs. To address these problems, we present a distributed dynamic μFirewall architecture based on mobile agents and KeyNote trust management system. In this architecture, KeyNote trust management system provides the scalable distributed control capability and supports a mechanism called “policy-updates on demand”. Mobile agents implement dynamic security policy reconfiguration and enhance the scalability. Each μFirewall is built with a packet filter and DTE-enhanced evaluator to enforce policy at the end points. A distributed intrusion detection and response (DIDR) system supports dynamic security capabilities and provides fast response to attacks from all possible sources. Our architecture is scalable, topology independent, and intrusion-tolerant.