Socket.IO is a JavaScript library for real-time, bidirectional communication between a client and a server. It usually runs over HTTP and upgrades to a persistent connection, which makes it useful for chat apps, live dashboards, and collaborative tools. Because it supports low-latency messaging and event-based traffic, it can also be attractive to attackers.
In malware operations, Socket.IO may be used for command-and-control (C2) channels that look like normal web application traffic. That can help malicious traffic blend in with legitimate browser or app connections, especially if it uses common ports and repeated small messages. Defenders should watch for unexpected Socket.IO endpoints, unusual outbound connections from endpoints that do not need them, and strange event names or message patterns. Network filtering, endpoint telemetry, and allow-listing approved services can make this kind of C2 easier to spot and block.