The security of Sixth Generation (6G) technology and its services have been a focal point for industry, academia, and governments. To safeguard this emerging technology from cyber threats, new security mechanisms that utilize Artificial Intelligence (AI) and zero trust approaches have been proposed for securing the wireless and mobile networks against smart attacks. In this article, we present an analysis of current research efforts on the 6G network security, focusing on the use of AI algorithms and Zero Trust Architecture (ZTA), and we identify their shortcomings and limitations. To overcome these gaps, we propose a new 6G security framework based on ZTA that employs adaptive AI algorithms executed by additional entities named hierarchical defense agents. These agents will enhance the security of the 6G network, its components, and its services.