An improved arrangement for controlling access to data files by computer users. Access permission bits are used in the prior art to separately indicate permissions for the file owner and nonowners to read, write and execute the file contents. An additional access control bit is added to each executable file. When this bit is set to one, the identification of the current user is changed to that of the owner of the executable file. The program in the executable file then has access to all data files owned by the same owner. This change is temporary, the proper identification being restored when the program is terminated.