In setup>options>Spam Management scroll down to where you see "Maximum messages to check for spam" and make it '1'
Look down at "Spam Phrases" and insert this regex:
Code:
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And tick the "Manually approve" option. Then click "save" at the bottom of the page.
So that any first posts that contain links will go to approval queue. And since post count only counts published posts, the spammer can post any number of spam links and none of them will show except to you and your moderators.
You can get rid of the annoying notice that your post is awaiting approval by inserting this code in your extra.less template:
CSS:
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And click "Save."
So that legitimate new users aren't annoyed waiting for their post to be approved, and the spammer thinks he accomplished his task, and leaves.