Services also need explicit write permissions to write to resources, on a per-service basis. By using a write-restricted access token, only those resources which have to be modified by a service are given write access, so trying to modify any other resource fails. Services will also have pre-configured firewall policy, which gives it only as much privilege as is needed for it to function properly. Independent software vendors can also use Windows Service Hardening to harden their own services. Windows Vista also hardens the named pipes used by RPC servers to prevent other processes from being able to hijack them.