Cisco ASA 5520 adaptive security appliances are purpose-built solutions that combine best-in-class security and VPN services with an innovative, extensible services architecture. Designed as a core component of the Cisco Self-Defending Network, the Cisco ASA 5520 provides proactive threat defense that stops attacks before they spread through the network, controls network activity and application traffic, and delivers flexible VPN connectivity. The result is a powerful multifunction network security appliance that provides the security breadth and depth for protecting home office, branch office, small and medium-sized business, and enterprise networks while reducing the overall deployment and operations costs and complexities associated with providing this new level of security.