Wall Street Journal:

Government officials across the U.S. are using location data from millions of cellphones in a bid to better understand the movements of Americans during the coronavirus pandemic and how they may be affecting the spread of the disease.

The federal government, through the Centers for Disease Control and Prevention, and state and local governments have started to receive analyses about the presence and movement of people in certain areas of geographic interest drawn from cellphone data, people familiar with the matter said. The data comes from the mobile advertising industry rather than cellphone carriers.

The data—which is stripped of identifying information like the name of a phone’s owner—could help officials learn how coronavirus is spreading around the country and help blunt its advance. It shows which retail establishments, parks and other public spaces are still drawing crowds that could risk accelerating the transmission of the virus, according to people familiar with the matter. In one such case, researchers found that New Yorkers were congregating in large numbers in Brooklyn’s Prospect Park and handed that information over to local authorities, one person said. Warning notices have been posted at parks in New York City, but they haven’t been closed.

It would be better if this data collection were more out in the open and less murky. We have to be wary of giving up liberties in search of security.