In the course of the pandemic with lockdown restrictions in place, the CDC (Centers for Disease Control and Prevention) secretly kept track of Americans’ travel and locations, as per documents obtained via a Freedom of Information Request. The CDC acquired aggregated locations from a firm that collects data about users from mobile apps. Although the data is anonymous, it's fairly easy to connect it with individuals.
The CDC claimed that the information “has been critical for ongoing [COVID] response efforts, such as hourly monitoring of activity in curfew zones.” The CDC has also provided a variety of applications that could benefit from the data, such as “monitoring adherence to state-level policies to quarantine after arrival from another state.”
Even post-pandemic, the CDC has stated that it will make use of this data to serve a variety of other purposes, including the prevention of violence, because that falls within their health policy as well.