Modular construction is a design approach built from repeatable parts that can be rearranged, replaced, or combined in different ways. Instead of creating one monolithic system, builders use smaller components with clear jobs and interfaces. This makes it easier to prototype, test, repair, and adapt a design without rebuilding everything from scratch.
In cyber security, modular construction matters because the same idea appears in both attacks and defenses. Malware may be split into modules such as a loader, persistence component, credential stealer, or data exfiltration tool, letting attackers update one part without changing the whole payload. Defensive tools use the same pattern for flexibility: agents, detection rules, response playbooks, and log collectors can be swapped or extended as needs change. Modular systems are powerful, but they also create risks if one weak component becomes the entry point for compromise.