Nagios Support Forum

I noticed that the NCPA agent runs as root when installed on RHEL. Is there a need for a nagios account and if so what is it's purpose?

I believe initially, ncpa was intended to be run as nagios (with elevated privileges), that's why you can still see in the the "/usr/local/ncpa/etc/ncpa.cfg":
I think, if you change these lines (for the listener & passive) to:
you could safely remove the nagios user and nagcmd group.

Note: I did this on my test box, and I am still able to monitor it just fine.

Would it be more secure to have the listener run as nagios rather than root?

Yes it would, putting application access on a more restricted account would be more secure. I'm not sure if it is intended to have it install as root, I'll have to check into that.