A method for detecting a man-in-the-middle attack against communications between a client device and a specific remote end point over a network, the method using probe software installed on the client device, the method comprising the probe software sending a connection initiation request from the client device over the network, directed to the remote end point, to at least partially initiate a secure network connection between the remote end point and the client device, receiving at the client device encryption credentials sent to the client device in response to the connection initiation request, the probe software comparing the received encryption credentials with expected encryption credentials for the remote end point, and the probe software determining that a man-in-the-middle attack is present if the received encryption credentials do no match the expected encryption credentials.