A software-defined perimeter (SDP), sometimes referred to as a black cloud, is a method of enhancing computer security. The SDP framework was developed by the Cloud Security Alliance to control access to resources based on identity. In an SDP, connectivity follows a need-to-know model, where both device posture and identity are verified before access to application infrastructure is granted. The application infrastructure in a software-defined perimeter is effectively "black"—a term used by the Department of Defense to describe an undetectable infrastructure—lacking visible DNS information or IP addresses.[dubious – discuss] Proponents of these systems claim that an SDP mitigates many common network-based attacks, including server scanning, denial-of-service, SQL injection, operating system and application vulnerability exploits, man-in-the-middle attacks, pass-the-hash, pass-the-ticket, and other attacks by unauthorized users.