JEFFREY BROWN:

September 11, 2014, there is an explosion at a chemical factory in St. Mary Parish in Louisiana. The video is soon posted on YouTube, Twitter is flooded with chatter, including screen shots of news Web sites, a local TV station, and, it appears, CNN's.

A video surfaces of ISIS taking responsibility for the explosion and local residents receive text messages warning them of toxic fumes in the area. Big news, except there was no explosion, the video was a fake, as were the news Web sites that reported it, and the footage of the Islamic State group taking credit.

The social media posts were not what they seemed. As reported in a cover story in The New York Times Magazine, it was all the work of the Internet Research Agency, a shadowy Russian organization based in a nondescript building in Saint Petersburg.

Adrian Chen wrote the story. He joins me now.

Welcome to you, Adrian.

This is a very bizarre tale that you have written. Tell us, what is the Internet Research Agency? How much do we know about it?