WebSocket-over-HTTPS is a way to keep a WebSocket session inside an HTTPS connection. The client and server start with normal encrypted web traffic, then maintain a long-lived, bidirectional channel for sending messages in real time. Because the session is encrypted and uses common web ports and patterns, it can look similar to ordinary browser or application traffic.
In cyber attacks, malware and operator tools use this channel for command-and-control, data theft, or tasking a host without opening a noisy custom port. That makes filtering harder for perimeter devices that mainly inspect destination, port, or basic reputation. Defenders often need endpoint telemetry, TLS inspection where permitted, proxy logs, and application-specific audit records to spot unusual WebSocket behavior such as long-lived sessions, unexpected destinations, or repeated small encrypted messages. Used properly, the same mechanism is also a normal part of many legitimate web apps, which is why behavior-based detection matters.