The following configuration files are privileged regardless of their ownership:
/etc/ppp/options
/etc/ppp/options.ttyname
/etc/ppp/peers/peer-name
The file $HOME/.ppprc is owned by the user. Options that are read from $HOME/.ppprc and from the command line are privileged only if the user who is invoking pppd is root.
Arguments that follow the file option are privileged.