I have a shared server (root access) using Cpanel / Centos with suphp enabled.
Twice this week the sever's load skyrocketed and was unable to login to trace teh cause, had to reboot instead.
After reboot, I went to whm > CPU/Memory/MySQL Usage and saw nothing in red aside netstat (21% cpu). I'm not sure if this is the cause, but how can I trace the absolute user or script causing this spike?
Right now, your effort should be focused on getting the box stabilized. Drop your HTTP MaxClients to a reasonable number (maybe 250 or less depending on how much memory you have). Limit the number of emails domains are allowed to send per hour. Follow this guide to understand what happened the last time your server had to be rebooted: