WAF Deployment Guide + A Free Tool That Works

WAF, short for Web Application Firewall, is a security layer that protects web applications by filtering and monitoring HTTP traffic. It’s specifically designed to prevent common web attacks such as SQL Injection and Cross-Site Scripting (XSS).

In general, WAFs come in three forms:

• Software WAFs (e.g., open-source or self-hosted)
• Hardware WAFs (appliances)
• Cloud WAFs (provided by CDN or security vendors)

In this article, we'll focus on deployment modes commonly used by hardware or appliance-based WAFs — and then introduce a free and modern WAF that’s easy to deploy.

Common WAF Deployment Modes

There are four main deployment modes for WAFs: Reverse Proxy, Transparent Proxy, Transparent Bridge, and Traffic Mirroring.

1. Reverse Proxy

A reverse proxy WAF acts as an intermediary between the client and the actual server. The client connects to the WAF, and the WAF forwards the request to the backend server. This makes the real server invisible to the client.

Client → WAF (Reverse Proxy) → Server

Advantages:

• The WAF has full control over HTTP(S) traffic.
• Easy to perform request/response inspection and rewriting.
• The real server's IP is hidden.

2. Transparent Proxy

A transparent proxy WAF intercepts traffic without modifying IP addresses. It typically sits inline between the client and server, making each side believe they are communicating directly.

Solid lines represent actual TCP connections, while dashed lines show perceived connections:

Client ———→ Transparent Proxy WAF ———→ Server
   ↖︎——————————————↗︎
     (perceived connection)

Key features:

• No IP configuration changes required.
• Acts invisibly to both ends.
• Requires physical inline deployment (cable-level interception).

3. Transparent Bridge

Unlike transparent proxies, a transparent bridge WAF does not participate in the TCP handshake. It simply analyzes traffic without modifying or terminating connections.

It’s deployed inline just like a transparent proxy, but functions more like a passive observer.

Benefits:

• Truly “plug-and-play”: doesn’t interfere with TCP logic.
• Can be inserted or removed without interrupting traffic.
• More stable in case some traffic bypasses the WAF.

4. Traffic Mirroring

When inline deployment isn’t possible — for example, in production networks that can't be altered — traffic mirroring can be used.

In this mode, a switch copies HTTP(S) traffic and sends a mirrored stream to the WAF:

Client ↔ Switch ↔ Server
            ↘
           WAF (receives mirrored traffic only)

The WAF inspects the mirrored traffic but does not interfere with the original communication.

Pros:

• Completely non-intrusive.
• Zero impact on production flow.
• Great for passive monitoring or alerting.

Comparison of Different Modes

A Free and Reliable WAF You Should Try: SafeLine

If you’re looking for a lightweight, open-source, and self-hosted WAF, I highly recommend trying SafeLine by Chaitin Tech.

SafeLine is:

• Free to use, with no feature limitations.
• Docker-deployable with one command.
• Capable of semantic analysis (far beyond regex filtering).
• Actively maintained and trusted by 300,000+ deployments.

You can deploy it on your own server and get full control over web traffic protection. It supports common WAF deployment modes (reverse proxy, transparent, mirroring, etc.), and has a clean web dashboard for rule management and log inspection.

👉 - GitHub Repository

👉 - Official Docs

👉- Discord Community

Whether you're building personal projects or managing production workloads, understanding WAF deployment modes — and having access to powerful free tools like SafeLine — is a great step toward modern web security.

Stay safe out there!