Devices, systems, and methods of detecting whether an electronic device or computerized device or computer, is communicating with a computerized service or a trusted server directly and without an intermediary web-proxy, or indirectly by utilizing a proxy server or web-proxy. The system searches for particular characteristics or attributes, that characterize a proxy-based communication session or channel and that do not characterize a direct non-proxy-based communication session or channel; or conversely, the system searches for particular characteristics or attributes, that characterize a direct non-proxy-based communication session or channel and that do not characterize a proxy-based communication session or channel; and based on these characteristics, determines whether or not a proxy server exists and operates.