1. A method for detecting that an online session is compromised, the method comprising: determining a session identifier for an online session between a first device and a second device over a network, wherein the session identifier is associated with a plurality of device fingerprints collected during the online session; receiving a first device fingerprint collected during the online session, wherein the first device fingerprint is collected at a first location of a first page; receiving a second device fingerprint collected during the online session, wherein the second device fingerprint is collected at a second location of a second page, where the first page and the second page comprise different content; determining, based at least in part on a comparison between the first device fingerprint and the second device fingerprint, a presence of a third device during the online session which indicates an interference of the online session between the first device and the second device by the third device; and providing an alert indicating the interference of the online session based at least in part on a determination of the presence of the third device during the online session.