Today, I’ve learned that even if you untick the setting “Allow link notifications from other Weblogs (pingbacks and trackbacks)”, that will only apply to all new posts and not the older ones which are getting bombarded. Thanks Ed Pham. Nevertheless, I’ve unchecked that.
Reading Shelley’s post, I’m just going to take her advice and moderate everything until someone can find a way to combat trackback spam. It’s under Options > Discussion > Before a comment appears: “An administrator must approve the comment (regardless of any matches below)”. Check that option for now. It’ll be a pain, but hopefully for just a short amount of time.