Mobile Agent (MA) technology raises significant security concerns and requires a thorough security framework with a wide range of strategies and mechanisms for the protection of both agent platform and mobile agents against possibly malicious reciprocal behavior. The security infrastructure should have the ability to flexibly and dynamically offer different solutions to achieve different qualities of security service depending on application requirements. The chapter presents the security threats that typically arise in MA applications and describes the proposed currently available countermeasures to protect both nodes and mobile agents. In addition, the chapter surveys the state-of-the-art research activities about integrated security supports in MA systems and identifies open research issues and on-going research work.