Excessive resource usage: rpcuser

[ZeroNine]

Hi,
I been running my server without any issues for over a year now.
Starting a couple days ago I started receiving this: Excessive resource usage: rpcuser every hour out of no where.
I understand I can add this to the ignore list but I just wanted to see if anybody knows if this is some kind of hacking attempt or if the server may be compromised in any way.

Thanks for any help.

[ZeroNine]

I forgot to mention I am also receiving this email now along with the previous:
Suspicious process running under user rpcuser

Executable:

/usr/sbin/rpc.statd


Command Line (often faked in exploits):

/usr/sbin/rpc.statd --no-notify