WAF stands for Web Application Firewall.

It’s a security layer that protects web applications from common web-based attacks such as SQL injection, Cross-Site Scripting (XSS), Cross-Site Request Forgery (CSRF), and others.

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🔍 In Simple Terms

A WAF sits between your web application and the internet — it monitors, filters, and blocks malicious HTTP traffic before it reaches your server.

[User] → [WAF] → [Web Application Server]

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⚙️ How It Works

A WAF:

• Inspects incoming requests to your web app (headers, URLs, payloads, etc.).
• Applies security rules (predefined or custom) to detect suspicious patterns.
• Blocks, challenges, or logs the request if it looks malicious.
• Allows legitimate traffic to pass through.

Example:

• If someone tries to send this in a form field:

  ' OR 1=1 --
  

  → A WAF can detect it as a SQL injection attempt and block the request.

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🧩 Types of WAF

1. Network-based WAF

   • Installed on-premise, close to the web server.
   • High performance, but expensive.

2. Host-based WAF

   • Runs as a software plugin on the same server as the application.
   • Flexible but consumes server resources.

3. Cloud-based WAF (most common today)

   • Offered by providers like AWS WAF, Cloudflare, Akamai, Azure WAF.
   • Easy to deploy, scalable, and managed for you.

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🛡️ Common Attacks WAF Protects Against

• SQL Injection
• Cross-Site Scripting (XSS)
• File Inclusion attacks
• Command Injection
• Cross-Site Request Forgery (CSRF)
• DDoS (to some extent, depending on WAF capabilities)
• Zero-day exploits (using heuristic or behavior-based detection)

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📈 Benefits

✅ Protects web apps from known vulnerabilities ✅ Helps meet compliance requirements (e.g., PCI DSS) ✅ Reduces load on backend servers by filtering malicious requests early ✅ Provides logging and analytics for suspicious traffic

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