File permissions indicate what kind of access is granted to users on a system. There are three types of permission (the ability to read, write, or execute) and there are three categories of users (the file's owner, users who are in the file's group, and everybody else on the system, with the exception of the superuser). When using NFS, and when using the underlying RPC protocol, it is possible for unauthorized users to obtain unintended access to files.
It should be noted that the semantics of using commands which change the permissions mode of a file, the owner of a file, or the group ownership of a file differ slightly when using NFS than when using a local file system. Often with distributed file systems, caching is used to increase performance. If caching is used, then the effects of changing the permissions mode of a file, the owner of a file, or the group ownership of a file may not take effect immediately on the remote file system.