In one aspect, the present disclosure relates to a method including: determining whether first data representative of a first string of content used by a user to access an application is present within the data structure having positions that contain values representative of strings of content; responsive to determination that the first data is not present within the data structure, retrieving a value from an index using a key associated with the user, the value being derived from positions in the data structure that contain values representative of a second string of content previously used by the user to access the application; decrementing the values of the positions in the data structure representative of the second string of content to remove second data representative of the second string of content from the data structure; and adding the first data representative of the first string of content to the data structure.