Software Secure Firewall Threat Defense
Platform Secure Firewall Threat Defense Virtual
Activity Onboard

Advanced Network Analysis and Preprocessing Transport and Network Layer Preprocessors The Packet Decoder

Last updated: Jul 29, 2025

The Packet Decoder


 

This section applies to Snort 2 preprocessors. For information on Snort 3 inspectors, see https://www.cisco.com/go/snort3-inspectors.

Before sending captured packets to a preprocessor, the system first sends the packets to the packet decoder. The packet decoder converts packet headers and payloads into a format that preprocessors and the rules engine can easily use. Each stack layer is decoded in turn, beginning with the data link layer and continuing through the network and transport layers.