A Web Application Firewall filters malicious HTTP traffic to reduce application exploits, but secure coding and timely patching remain essential.
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Background for this topic.
A Web Application Firewall (WAF) filters HTTP(S) traffic between clients and a web application, applying signatures, behavioral rules, rate limits, and custom policies. It can block or challenge requests resembling SQL injection, cross-site scripting, path traversal, malicious file uploads, or some abusive automation before they reach application code. WAFs may run as cloud services, network appliances, or software, but their security function is the same: reduce the attack surface of publicly reachable application endpoints.
A WAF is a control layer, not a substitute for secure coding, authentication, authorization, or patching. It may miss attacks that use valid requests, business-logic abuse, or novel payloads, and poorly tuned rules can block legitimate users or leave bypasses. Organizations should terminate or otherwise inspect encrypted traffic where appropriate, keep rules aligned with application changes, review alerts and blocked requests, and use WAF rules as temporary compensating protection while vulnerable components are fixed. Its logs can also support investigation and vulnerability prioritization.
Organizations that rely on their content delivery network provider for Web application firewall services may be inadvertently leaving themselves open to attack.