vBulletin Forum Causing High Load or high CPU usage
If you have created your site using a Vbulletin forum and are experiencing high load or CPU issues we recommend you read the vBulletin forums http://www.vbulletin.com. These forums contain numerous bits of advice from others who have similar issues with vBulletin installations.
In particular, we suggest:
1) Disable Search.
2) Enable Persistent Database Connections
3) Turn off any extra stats recorders,
Other specific examples:
If you believe your account was hacked: