Cisco ASA (Adaptive Security Appliances) are easy-to-deploy solutions that integrate world-class firewall, Unified Communications (voice/video) security, SSL and IPsec VPN, intrusion prevention (IPS), and content security services in a flexible, modular product family.
Like the Cisco PIX firewalls, the ASAs are based on Intel x86 architecture. The ASA series of devices run PIX code 7.0 and later. Through PIX OS release 7.x the PIX and the ASA use the same software images.
Beginning with version PIX OS version 8.x, the codes diverge, with the ASA using a Linux kernel and PIX continuing to use the traditional Finesse/PIX OS combination.