A method of detecting whether a computer file has been copied, the computer file comprising a software program and having an inode number. The inode number of the computer file is retrieved by the software program. From the computer file, a stored inode number is read, the stored inode number being the inode number of a file system from which the computer file should not be copied. The retrieved inode number and the read inode number are compared and it is determined that the computer file has been copied if the retrieved inode number does not match the read inode number. Also provided are a method of enabling detection of the copying of a computer file, and devices and software program products corresponding to the methods.