Content-ID is the core of Palo Alto Networks' prevention architecture, providing single-pass application layer inspection to deliver real-time threat prevention across all traffic.

''Content-ID uses a single-pass architecture to perform application-layer (Layer 7) traffic inspection and real-time threat prevention. Unlike traditional firewalls that rely on multiple scans, Content-ID inspects traffic once to enforce multiple security controls simultaneously.''

(Source: Content-ID Overview)

By consolidating security functions in a single pass, it ensures both efficiency and comprehensive security.