Open Source Web Application Firewall with Zero-Day Detection and Bot Protection

From zero-day exploits to massive bot attacks, the demand for powerful, self-hosted, user-friendly web application security solutions has never been stronger.

SafeLine is currently GitHub’s most star open source web application firewall (WAF), with stars of over 16.4K and a rapidly growing global user base.

This walkthrough covers what a safeline is, how it works, and why it becomes a more reliable solution than a cloud-based WAF.

What is Safeline WAF?

SafeLine is a self-hosted web application firewall that acts as a reverse proxy, filtering, and monitoring of http/https traffic that blocks malicious requests before reaching the backend web application. Unlike cloud-based WAFs, Safeline runs entirely on its own server. This induces unparalleled vision and data sovereignty.

Key features of Safeline WAF

Comprehensive Attack Prevention

SafeLine effectively blocks a wide range of common and advanced web attacks, including SQL Injection (SQLI), Cross-Site Scripting (XSS), OS Command Injection, CRLF Injection, XML External Entity (XXE) Attacks, Server-Side Request Forgery (SSRF), and Directory Terversal.

Zero-Day Detection with Semantic Analysis

Unlike traditional signature-based WAFs, Safeline uses a patented semantic analysis engine that deepens HTTP traffic semantics.

This approach provides a highly accurate and complex zero-day and zero-day attack detection, resulting in an industry-leading detection rate of 99.45% and an ultra-low positive positive rate of 0.07%. (The chart below compares two versions of open source WAFs that are globally recognized as safelines.)

Robust bot protection

Safeline offers comprehensive defense-in-depth protection against automated bot attacks, credential stuffing, malicious rubs, stock hoarding, and increased threat vectors involved in vulnerability scans.

It combines some powerful mechanisms outside the box:

• Captcha’s Challenge: It is issued dynamically to distinguish human users from automated clients, particularly in suspicious or risky traffic scenarios.
• Dynamic protection: Randomly encrypt and confuse frontend code, such as HTML or JavaScript, before delivering it to the client. This prevents bots from parsing the page structure and interacting with DOM elements, effectively rendering automated scripts.
• Replay prevention mechanism: It often detects and blocks reuse of tokens, headers, or payloads that are leveraged in script attacks or qualification-filled stuffing campaigns.

HTTP Flood DDOS Relaxation

HTTP Flood DDOS attacks attempt to overwhelm the server by sending large numbers of HTTP requests in a short period of time. These attacks can run out of server resources, slow performance, and allow applications to take completely offline.

To counter this, we implement a safe line Rate Limit To request frequency and reduce abuse. These measurements are highly configurable and allow the defender to adjust the threshold based on the actual traffic pattern.

In the case of sudden traffic spikes, whether legitimate or malicious Virtual waiting room mechanism. This ensures service availability by keying in and slowly releasing excessive users, preventing backend overload while maintaining a fair and orderly access experience.

Authentication challenges

Safeline is designed with the principle of trust in mind. We don’t always verify trust. Provides configurable Visitor authentication to secure access to protected applications, enhancing security through implemented identity checks.

As a built-in identity gateway, it supports modern authentication protocols such as OIDC and integrates seamlessly with identity providers such as GitHub.

SafeLine supports Single Sign-On (SSO) to streamline user authentication and simplify the login experience in the meantime.

Above all, these enterprise-grade identity features are included for free.

A simple development in just a few minutes

Safeline is designed for quick setup and easy management. You must install and run the following environment:

• Operating System: Linux (X86_64 or ARM64)
• Dependencies: Docker (version 20.10.14 or later) and Docker Compose (version 2.0.0 or later)
• Minimum system requirements: 1 CPU core, 1 GB of RAM, 5 GB of available disk space

Once your environment is ready, one command will take several minutes to install.

bash -c "$(curl -fsSLk https://waf.chaitin.com/release/latest/manager.sh)" -- --en

A user-friendly wizard-based interface guides you through configuration. The full documentation is available here.

Why choose a safeline over a cloud-based WAF?

Unlike traditional cloud-based WAFs that route traffic through third-party infrastructure, Safeline offers full deployment autonomy. Here are the advantages:

• Complete Data Control: Sensitive traffic and logging remain on-premises, reducing exposure to third-party cloud risks.
• Cost-efficient: Regular subscription fees, common to cloud WAFs, are particularly beneficial in high traffic environments.
• Free and Box Out Enterprise Features: What’s behind the “premium” tier elsewhere, such as advanced threat detection, bot protection, identity authentication, and more, is outside the box and included for free.

The best use case for the safelines

Safeline is a versatile solution built to suit a wide range of web application security needs. Particularly suitable:

• Organizations with strict data privacy or regulatory compliance requirements
• Sophisticated bots and automated threat target teams
• Small businesses seeking affordable enterprise-grade protection
• DevOps and Security Teams Requires Full Deployment Control and Customization
• Projects that require rapid deployment and simple maintenance

The final words

Safeline stands out as a powerful, open source alternative to traditional cloud-based WAFs. State-of-the-art zero-day detection, robust bot mitigation, and zero-trust identity capabilities (all bundled in self-hosted, easy-to-deploy packages) allow developers, security teams, and organizations of all sizes to control web security.