It's a pleonasm: https://en.wikipedia.org/wiki/Pleonasm

ATM Machine = Automated Teller Machine Machine.

"ATM" machine: "automatic teller machine" machine

The phrase "PAM Module" would be expressed in full as "Pluggable Authentication Module Module".

the M in PAM stands for Module, so saying PAM module is redundant (like saying ATM machine, where the M stands for Machine)