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What Is Web Application Firewall?

Updated at: Sep 28, 2021 GMT+08:00

Web Application Firewall (WAF) keeps web services stable and secure. It examines all HTTP and HTTPS requests to detect and block the following attacks: Structured Query Language (SQL) injection, cross-site scripting (XSS), web shells, command and code injections, file inclusion, sensitive file access, third-party vulnerability exploits, Challenge Collapsar (CC) attacks, malicious crawlers, and cross-site request forgery (CSRF).

How WAF Works

After purchasing WAF, add the website to WAF on the WAF console. After a website is connected to WAF, all website access requests are forwarded to WAF first. WAF detects and filters out malicious attack traffic, and returns normal traffic to the origin server to ensure that the origin server is secure, stable, and available.

Figure 1 How WAF protects a website

The process of forwarding traffic from WAF to origin servers is called back-to-source. WAF uses its back-to-source IP addresses to send received client requests to origin servers. In this way, origin servers communicate with WAF back-to-source IP addresses instead of client IP addresses. So the original servers become invisible for the client.

Figure 2 Back-to-source IP address

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