The Cisco PIX 501 Security Appliance delivers a multi layered defense for small office network environments through rich, integrated security services, including stateful inspection firewall services, advanced application and protocol inspection, site-to-site and remote access VPN, in-line intrusion prevention, and robust multimedia and voice security-all in a single, integrated solution.

Cisco PIX Security Appliances incorporate Cisco Adaptive Security Algorithm, which provides stateful inspection firewall services by tracking the state of all authorized network communications and by preventing unauthorized network access. As an additional layer of security, Cisco PIX Security Appliances integrate over two dozen purpose-built inspection engines that perform in-depth Layers 4-7 inspection of network traffic flows for many of today's popular applications and protocols. To defend networks from application layer attacks and to give businesses more control over applications and protocols in their environment, these inspection engines incorporate extensive application and protocol knowledge and employ security enforcement technologies that range from protocol conformance checking, application and protocol state tracking, Network Address Translation (NAT) services, and attack detection and mitigation techniques such as protocol field length checking and URL length checking.

Administrators can easily create custom security policies using the many flexible access control technologies provided by Cisco PIX Security Appliances including network and service object groups, turbo access control lists (ACLs), user- and group-based policies, and more than 100 predefined applications and protocols. By combining these flexible access control technologies with the powerful stateful inspection firewall services and advanced application and protocol inspection services that Cisco PIX Security Appliances provide, businesses can easily enforce their network security policies and protect their networks from attack.

The integrated in-line intrusion prevention capabilities of the Cisco PIX 501 Security Appliance can protect small office networks from many popular forms of attacks, including Denial-of-Service (DoS) attacks and malformed packet attacks. Using a wealth of advanced intrusion-prevention features, including DNSGuard, FloodGuard, FragGuard, MailGuard, IPVerify, and TCP intercept, in addition to looking for more than 55 different attack "signatures," Cisco PIX Security Appliances keep a vigilant watch for attacks, can optionally block them, and can provide real-time notification to administrators.