Invest in ML to spot patterns. I don't know specifically how it was done, but I heard that Whatsapp had a hard time with spam after e2e encryption since you cou

Invest in ML to spot patterns. I don't know specifically how it was done, but I heard that Whatsapp had a hard time with spam after e2e encryption since you couldn't catch spam by examining the text. So instead they started looking for patterns and found things like an account that was less than a week old sending out thousands of messages a week. It's an outlier in usage pattern. I believe credit card fraud systems do something similar. Like if you suddenly make a purchase far far away or in a category that you never do, then it gets flagged. I'm happy to help brainstorm more ideas.