A server instance is a virtual server created and run on cloud infrastructure. It behaves like a standalone computer, with its own operating system, applications, and allocated resources, while sharing underlying physical hardware with other instances. Providers may count instances separately from the physical machines that host them.
In cybersecurity, instance counts help describe the possible scale of an incident, but they do not directly reveal how many customers, files, or systems were compromised. Attackers may target an instance to install malware, steal credentials, or access data; defenders investigate each affected environment using available logs, process records, and network activity. Cloud providers and customers may hold different parts of the evidence, so interpreting an instance total requires care.