Yup, Ms Sheryl Sandberg yelled at me. It was the day after I briefed Facebook's board of directors on an unprecedented and troubling finding on our platform. Combing through billions of accounts, my colleagues and I had discovered a web of fake personae that we could confidently tie to Russia.

I told the board the difficult truth: I had no confidence that we'd found out everything the Russians were up to, and it was quite possible that things would get worse before we built the teams and invented the technology necessary to stop it.