Adaptive systems dynamically change their behavior or structure at runtime to respond to environmental changes. This paper considers one class of adaptive systems-those that adapt application-level security mechanisms. Nowadays, adaptive software security is gaining greater attention as a way to balance the tradeoff between systems security and IT infrastructure overhead. Several adaptive security systems have been developed recently supporting hardware-level to application-level reconfiguration. This paper surveys four adaptive application-level security systems and evaluates them in terms of how well they support critical security services (i.e. authentication, authorization, and tolerance) and what level of adaptation they achieve. Based on our evaluation results, we provide recommendations for future research.