A content delivery network (CDN) is a distributed set of servers that stores and serves files from locations close to users. For large downloads, game patches, and other heavy assets, a CDN reduces latency and prevents a single origin server from being overwhelmed by traffic spikes.
In cyber security, CDNs matter because they sit on the front line of delivery. Defenders use them to absorb distributed denial-of-service traffic, enforce TLS, add web application filtering, and verify that updates are delivered through signed or controlled URLs. Attackers can also abuse CDNs or look alike infrastructure to hide malicious hosting, distribute trojanized installers, or blend harmful traffic into ordinary web requests. In practice, secure CDN use is about both performance and trust: fast delivery is useful only if the files, routing, and access controls remain intact.