There is some previous discussion about this regarding Facebook here: https://news.ycombinator.com/item?id=28119372 https://news.ycombinator.com/item?id=2811937

There is some previous discussion about this regarding Facebook here: https://news.ycombinator.com/item?id=28119372 https://news.ycombinator.com/item?id=28119372 The false positive rate does not look great.