The present disclosure provides systems and methods for automatically detecting third-party re-identification of anonymized computing devices. The method includes retrieving a log of content items provided to anonymized computing devices identifying a first content item provided to a plurality of anonymized computing devices within a first predetermined time period; for each anonymized computing device of the plurality of anonymized computing devices, generating a set of identifications of second content items retrieved by the anonymized computing device prior to receiving the first content item within a second predetermined time period; determining that signals or combinations of signals with a highest predictive ability between a first set of identifications and a second set of identifications exceeds a threshold; identifying a provider of the first content item; and if the signals or combinations of signals with the highest predictive ability exceeds the threshold, preventing, transmission of a request of an anonymized computing device for a content item to the identified provider.