Evaluating communications via a computer network for the presence of proxy-based communications, by sending to a computer via a computer network multiple data packets followed by an out-of-sequence data packet that is out-of-sequence relative to any of the multiple data packets, receipt of the out-of-sequence data packet configured to cause the computer to send an acknowledgement via the computer network, and to cause the requestor to send a second data request via the computer and the computer network, detecting receipt of the acknowledgement at a first time, detecting receipt of the second data request at a second time, calculating a time delay between the first time and the second time, performing the sending, detecting and calculating steps multiple times for calculating multiple time delays, and determining whether the requestor is communicating via a proxy by evaluating the multiple time delays with respect to a predefined proxy evaluation criterion.