Snort 3 — Open-Source Network Intrusion Detection and Prevention System

Introduction

Snort 3 is a next-generation network intrusion detection and prevention system that analyzes network traffic in real time. Originally created in 1998, Snort is one of the most widely deployed IDS/IPS platforms. Version 3 is a ground-up C++ rewrite with multithreading, a Lua configuration language, and a modern plugin architecture.

What Snort 3 Does

• Inspects live network traffic or pcap files for malicious patterns and protocol anomalies
• Matches packets against a database of community and commercial rule sets (Snort rules)
• Operates in IDS mode (passive detection) or IPS mode (inline blocking)
• Reassembles TCP streams and decodes application-layer protocols (HTTP, DNS, SMB, etc.)
• Logs alerts in multiple formats including JSON, syslog, and unified2

Architecture Overview

Snort 3 uses a pipeline architecture: packet acquisition (DAQ) feeds raw packets into decoders, which normalize protocols and hand off to the detection engine. The detection engine evaluates rules using a multi-pattern matcher (hyperscan or AC-full) against the reassembled stream. Inspectors are protocol-specific plugins that decode HTTP headers, extract file data, or track application state. The entire pipeline is multithreaded, with each packet thread processing independently.

Self-Hosting & Configuration

• Configuration uses a Lua script (snort.lua) instead of the legacy conf format
• Install community rules from snort.org or use Cisco Talos subscription rules
• Deploy inline using the DAQ afpacket or NFQ module for IPS (blocking) mode
• Tune performance with the max-threads setting and pin threads to CPU cores
• Output alerts to JSON for consumption by SIEMs like Elasticsearch or Splunk

Key Features

• Multithreaded packet processing for line-rate inspection on multi-core systems
• Lua-based configuration and rule scripting for dynamic detection logic
• Hyperscan regex engine integration for high-speed pattern matching
• File identification and extraction for malware analysis and policy enforcement
• Plugin architecture for custom inspectors, loggers, and IPS actions

Comparison with Similar Tools

• Suricata — multi-threaded IDS/IPS with EVE JSON logging; Snort 3 adds Lua scripting and the Talos rule ecosystem
• Zeek (Bro) — network analysis framework focused on logging and scripting; Snort focuses on signature-based alerting
• OSSEC/Wazuh — host-based IDS; Snort operates at the network level inspecting packets on the wire
• Falco — cloud-native runtime security for containers; Snort inspects traditional network traffic

FAQ

Q: What is the difference between Snort 2 and Snort 3? A: Snort 3 is a full C++ rewrite with multithreading, Lua configuration, a plugin architecture, and improved protocol inspection. Snort 2 rules are largely compatible.

Q: Can I use Snort as an IPS? A: Yes. Deploy it inline using the NFQ or afpacket DAQ module, and configure rules with drop, reject, or rewrite actions.

Q: Where do I get rules? A: Snort.org provides free community rules. Cisco Talos offers a registered (free, 30-day delay) and a subscriber (real-time) rule set.

Q: Does Snort 3 support hardware offload? A: Yes. It integrates with DPDK for high-speed packet capture and hyperscan for hardware-accelerated regex matching on supported CPUs.

Sources

• https://github.com/snort3/snort3
• https://www.snort.org/snort3