Ask HN: How do computers combat child pornography?

In this discussion, I want to put away the morality of the subject and have a programming discussion about the subject.

I remember a while ago I heard that google was using computer artificial intelligence to get rid of child pornography from their search results. Which it's very interesting from a technical perspective.

But the question becomes challenging when the computer has to figure out what looks like an adult or what looks like a child.

In this state of social media where young girls are mentally trained to show as much skin as possible. How do we teach bots to go through the process?