1. A system for using file hashes to track data leakage and document propagation in a network, comprising: one or more physical processors programmed to execute computer program instructions which, when executed, cause the physical processors to: obtain a set of hashes that are associated with files of a user device of a set of user devices, and a reference set of hashes that are associated with files of a reference system, wherein the reference system is limited to files authorized to be on all devices of the set of user devices; determine an additional subset of hashes included in the set of hashes and not included in the reference set of hashes based on a comparison between the set of hashes and the reference set of hashes; classify the user device into a group based on the additional subset of hashes comprising a hash that is the same as a hash associated with a file of at least another user device classified into the group; predict that the file associated with the same hash is exclusive for the group to which the user device is classified; scan one or more other user devices not classified into the group to determine what files are on the other user devices; generate an alert indicating unauthorized file access, wherein the alert is generated responsive to the scan indicating that the other user devices contain the file predicted to be exclusive for the group to which the user device is classified; and deliver the alert to a user.