NinjaFirewall is a Web Application Firewall to protect and secure WordPress. It works before the blog and its plugins are loaded, and offers unique security features not found in any other plugins. With more than 200 security rules, as many firewall policies and a powerful filtering engine able to detect WAF evasion techniques, it provides a strong level of security to WordPress. A free (WP Edition) and a premium (WP+ Edition) versions are available.
The premium WP+ Edition offers many additional options such as an advanced Access Control feature based on the user role, IP, geolocation, requested URI, user-agent, as well as a powerful rate limiting option, an anti-spam and a response body filter to scan the output of the HTML page before it is sent to the visitor (Web Filter). Although having already a fast filtering engine, it can also make use of Unix shared memory segments instead of the database to store its data for even quicker processing. Advanced firewall log and uploads management is another premium-only feature.
The premium WP+ Edition license starts at $29.90/year for one single domain or a whole multi-site network (regardless of the number of websites). Discounts are also available for bigger volumes.
NinjaFirewall runs only on Unix-like OS (Linux, BSD); it is not compatible with Microsoft Windows servers.