NETWORK SECURITY SYSTEM AND METHOD

In a security system for network communications with client devices, each client device has a communication module for communicating with at least one server over a network, a data storage module for storing one or more covert data values of one or more operational events at the client device, and a covert identifier generating module which creates at least one covert identifier based on the stored covert data values. The covert identifier is provided in one or more network messages to the server, or otherwise sent to the service provider, and may be provided in response to a specific request received over the network, or routinely in one or more messages normally involved in network communications. The server compares covert identifiers received from client devices having the same client identifier in order to detect possible clones.