WordPress causing high CPU utilization

Since a few days it turns out my blog is causing high CPU utilization for the PHP process. So much that my provider has given me two weeks to solve it. If not I have to “make alternative arrangements.” which comes down to four options:

1. Upgrade my package to the VPS Plan.
2. Upgrade my package to the Dedicated hosting plan.
3. Host somewhere else.
4. Give up this blog completely.

Here’s what I don’t get though, according to Google Analyctics I have only around 250 visitors a day. Anyway, here’s what i’ve done so far without any luck:

Installed WP-Supercache
Why: Instead of going through index.php it serves files directly by using rewrite rules in htaccess
Outcome: This seem to have relieved a small bit of the pain but I’m still averaging 70% CPU utilization.

Deactivate the Sociable plugin
Why: This was the only plugin I upgraded just 2 days before the mayhem started.
Outcome: Didn’t do anything

Added IP’s to htaccess to deny access
Why: It wasn’t only WordPress that caused high CPU, also my forum. When I checked the IP’s that accessed my forum it turned out that of the 441 IP that accessed my forum in Nov, approximately 132 were known forum spammers.
Outcome: Helped a little bit, more IP’s added

Blocked certain pages
Why: People were accessing the pages directly and they didn’t have any need for it
Outcome: Precise outcome unknown

Stopped saving of drafts
Why: I saw a long list of accessing the drafs, even when I wasn’t logged in
Outcome: Precise outcome unknown

Well the CPU utilization is under control right now. I’m not really sure what caused it. That’s the bad part of using a host without shell access, you can’t really see immediate effects on changes you make.

I believe the biggest problem was spammers hitting my blog, as it happened long after my initial increase of readers. I didn’t change anything around the day the problem started, except for the plugin upgrade which wasn’t the cause.