Disable Trackback sitewide

During the past 6 months, all trackbacks are spams. To save the resource of my server, I disable the trackback service sitewide.
I hope to see the CPU and Memory usage drop in the future.
There are still some problem of MovableType on Dreamhost.
Dreamhost is good. I use it for many small sites. But right now, I fell it is more restrict on memory usage. Any time I publish one post, 500 error comes. If rebuild site, situation worse.
I will keep watch it and see if it is getting better. Or I may transfer to VPS.