2 suspicious history entries while logged off

Hello. Today, I noticed 2 entries in Norton's security history that concerned me.

 

1.) High Disk Read usage by: Client Server Runtime Process

 

and

 

2.) High CPU Usage by: Host Process for Windows Services.

 

I believe I've seen these messages before. What concerns me is that these messages came up while no one was logged on the computer. Is is possible that these messages may be the result of normal background activity on the computer or could this be a hacker or virus? Thanks.