This article discusses security requirements for open distributed learning environments. Security is a critical issue, especially for highly interactive applications based on heterogeneous distributed architectures. In e-learning applications, security mechanisms have as their main purpose to protect against illegal access to information, so that confidentiality and integrity can be guaranteed. While a lot of efort in the e-learning domain has been put into delivering infrastructure and providing content, security issues have hardly ever been considered. Taking this fact into account, we have implemented a multiagent platform (the PMA3), which constitutes an open distributed infrastructure that addresses security issues. PMA3 is founded on multiagent principles and FIPA standards, and has been used in the development of e-learning environments.