mod_rewrite is an Apache HTTP Server module that rewrites request URLs or issues redirects according to rules. Administrators use it to normalize paths, enforce HTTPS, route traffic to different endpoints, or hide backend structure from users.
In cyber security, mod_rewrite matters because it sits directly in the request path and can change where a request goes before other controls see it. A bad rule can create open redirects, route sensitive paths to unintended handlers, or help attackers bypass access controls when assumptions about URL structure are wrong. When rewrite targets are built from user-controlled input, the risk increases sharply. Defenders review these rules as part of patching, because many Apache issues arise from the interaction between modules and configuration, not just the server binary. Careful allowlists, strict path matching, and testing after changes help keep rewrite logic from becoming an attack surface.