Hari Sreenivasan:

Over the past few weeks the city of Baltimore has essentially shut down online after a massive cyberattack followed by a ransom demand, which the city refuses to pay. But according to The New York Times, the malicious software known as EternalBlue used to attack Baltimore and many other cities and businesses around the world was created not by criminals but by the United States National Security Agency.

Reporter Scott Shane co-wrote The New York Times story. He joins us now via Skype from Baltimore. Thanks for being with us.

Tell us, what is this piece of software do?