What we know about Russia's social-media campaign provides lessons for the future.

Editor’s Note: The following is adapted from Jim Geraghty’s presentation earlier this week to the Austrian National Defense Academy, the Organization for Security and Cooperation in Europe, and the University of Vienna.

NRPLUS MEMBER ARTICLE I t is absolutely fair game and legal — in free countries, at least — for anyone to get online and say whatever he wants about American presidential candidates. If you want to say this candidate is a fool and that candidate is a bad guy, you’re perfectly free to do so.

What you cannot do is go online and pose as someone else. And if you’re a foreign intelligence service, we …