Apache Tomcat is an open-source Java servlet and JSP container. In practical terms, it provides the runtime layer that lets Java web applications receive requests, execute server-side code, and return responses. Many business applications, internal portals, and API services run on Tomcat or on systems that embed it.
Tomcat matters in cyber security because a flaw in the container can affect the availability and reliability of the applications it hosts. Attackers often look for exposed Tomcat services, outdated releases, weak administration controls, or known vulnerabilities that can crash a service, disrupt request handling, or help them gain deeper access. Defenders should inventory every Tomcat instance, track the exact version, and patch quickly when advisories are released. Monitoring for failed requests, repeated restarts, and unusual resource spikes can help distinguish normal maintenance from an active outage or abuse attempt.