A surveillance program called Data Analytical Services (DAS) has given law enforcement access to over a trillion US phone records annually for more than a decade, including those of innocent citizens and victims of crimes. The program, previously known as Hemisphere, operates in collaboration with AT&T and allows authorities to analyze call records using chain analysis, targeting not only suspects but also their contacts. Senator Wyden has expressed concerns about the legality of the DAS program and has received "troubling information" confidentially from the Department of Justice, prompting an investigation.