Open Source Go Firewall Software

CrowdSec - an open-source massively multiplayer firewall able to analyze visitor behavior & provide an adapted response to all kinds of attacks. It also leverages the crowd power to generate a global IP reputation database to protect the user network. Crowdsec shouldn't, and didn't crash any production so far we know, but some features might be missing or undergo evolutions. IP Blocklists are limited to very-safe-to-ban IPs only (~5% of the global database so far, will grow soon). A modern behavior detection system, written in Go. It stacks on Fail2ban's philosophy, but uses Grok patterns & YAML grammar to analyse logs, a modern decoupled approach (detect here, remedy there) for Cloud/Containers/VM based infrastructures. Once detected you can remedy threats with various bouncers (block, 403, Captchas, etc.) and blocked IPs are shared among all users to further improve their security. Crowdsec is an open-source, lightweight software, detecting peers with aggressive behaviors.

AgentGuard is a real-time protection layer designed to safeguard AI agents and applications from runaway execution, excessive costs, and unsafe behavior during interaction with large language model APIs. It works by intercepting API calls made by an AI system and continuously monitoring usage, including token consumption and associated costs, allowing developers to enforce strict budget limits. When predefined thresholds are reached, the system can automatically halt execution, trigger alerts, or gracefully terminate processes depending on the configured mode. This makes it particularly valuable in environments where agents operate autonomously and may enter unintended loops or inefficient workflows. The tool integrates directly into existing applications with minimal changes, often requiring only a few lines of code to activate protection. It also supports advanced configurations such as distributed tracking through Redis and webhook notifications for real-time monitoring.

SafeLine is a self-hosted WAF(Web Application Firewall) to protect your web apps from attacks and exploits. A web application firewall helps protect web apps by filtering and monitoring HTTP traffic between a web application and the Internet. It typically protects web apps from attacks such as SQL injection, XSS, code injection, os command injection, CRLF injection, LDAP injection, XPath injection, RCE, XXE, SSRF, path traversal, backdoor, brute force, HTTP-flood, bot abuse, among others. By deploying a WAF in front of a web application, a shield is placed between the web application and the Internet. While a proxy server protects a client machine’s identity by using an intermediary, a WAF is a type of reverse-proxy, protecting the server from exposure by having clients pass through the WAF before reaching the server. A WAF protects your web apps by filtering, monitoring, and blocking any malicious HTTP/S traffic traveling to the web application.

Coraza is an open-source, enterprise-grade, high-performance Web Application Firewall (WAF) ready to protect your beloved applications. It is written in Go, supports ModSecurity SecLang rulesets and is 100% compatible with the OWASP Core Rule Set. Coraza is a drop-in alternative to replace the soon-to-be abandoned Trustwave ModSecurity Engine and supports industry-standard SecLang rule sets. Coraza runs the OWASP Core Rule Set (CRS) to protect your web applications from a wide range of attacks, including the OWASP Top Ten, with a minimum of false alerts. CRS protects from many common attack categories including: SQL Injection (SQLi), Cross Site Scripting (XSS), PHP & Java Code Injection, HTTPoxy, Shellshock, Scripting/Scanner/Bot Detection & Metadata & Error Leakages. Coraza is a library at its core, with many integrations to deploy on-premise Web Application Firewall instances.