From LifeType Wiki
Name: Validate Trackback
Download link: http://sourceforge.net/projects/lifetype/files/
Author: Paul Westbrook
This plugin offers validation of trackbacks to prevent spam trackback.
When this plugin is installed, and a trackback is received, the plugin downloads the contents of the html pointed at by the url in the trackback, and looks for a trackback url. If it isn't able to download the html or is not able to find a trackback url, the trackback is deleted.
This catches most cases of spam trackback, where a spammer includes an url for a non-blog html page.
The plugin configuration page can be found under Control Center->Anti Spam Management.
Enable your Validate Trackback plugin in your pLog control center. That's all.