Hiding "secret" used in for PAM authentication

[Gregory Machin]

Hi.
We are using using PAM to authenticate users against Freeradius, an
that is working well. The problem is that the users are 3rd party
developers and some need root access. The issue we have is that the
radius secret is stored in clear text file. How can this be hidden so
that is can be misused  ?

Is there a document on hardening Freeradius ?


Thanks
G