Proxy detection systems and methods

A computing device, comprising:

• a communications interface;
• and
• a processor configured to:
• receive via the communications interface, from a client device, a first request to establish a transport-layer connection between the client device and the server, the first request containing a first source port number;
• in response to receiving the first request and prior to establishing the transport-layer connection, initiate a delay timer and withhold transmission of an acknowledgement to the first request until expiry of the delay timer;
• receive from the client device, prior to expiry of the delay timer, a second request to establish the transport-layer connection;
• in response to determining that the second request contains a second source port number matching the first source port number, initiate establishment of the transport-layer connection with the client device;
• and
• select, based on the determination, a handling action for the second request.