The process ID (PID) file must be properly secured.

The PidFile directive sets the path to the process ID file to which the server records the process ID of the server, which is useful for sending a signal to the server process or for checking on the health of the process. If the PidFile is placed in a writable directory, other accounts could create a denial of service attack and prevent the server from starting by creating a PID file with the same name.