Using a Linux box as a NAS

[Bill Tangren]

I am exploring how to use a Linux box as a Network Authentication Server. I've 
found a few VPN + PPP howtos, but I don't think that is quite what I need. The 
head of IT is looking to install something that will be the sole (2 factor) 
authentication point for our teleworkers for access to our internal network.

Could someone please point me to documentation that will explain how we can go 
about doing this?

Thanks!

Bill Tangren