A method of detecting whether data in a tape drive used in a file system is tampered is described according to one embodiment. The method includes the steps of: (a) preparing a first tape cartridge including a tape on which multiple files and archival records of index information are stored in a WORM partition, and index information is stored in the R/W partition; (b) reading and comparing the index information of the R/W partition and the last index information of the WORM partition; and (c) when these two pieces of index information do not match, determining that the index information of the R/W partition is tampered in case these two pieces of index information do not match.