Adaptive Security Algorithm

In Chapter 17, Adaptive Security Algorithm (ASA) was introduced as being the heart of the PIX Firewall system. Recognizing that ASA is more than just an algorithm for controlling the direction of traffic flows is important. ASA defines and controls all aspects and features of the PIX devices. While extremely powerful and versatile, ASA is less complex and more robust than packet filtering implementations. ASA provides performance and scalability advantages over application-level proxy firewalls.

ASA concepts introduced in this section, and covered in greater detail throughout this chapter, include the following:

• Security levels

• Stateful system

• Translations

• Connections