Report claims U.S. government is using cellphone location data to track undocumented immigrants

The Department of Homeland Security has bought a commercial database that tracks movements of "millions" of cellphones in America, and is using it to curb undocumented immigrants, The Wall Street Journal reported Friday, citing people familiar with the matter and documents it has seen. 
Such databases are legal in the U.S. and are typically used for commercial purposes, for example serving ads. But this is the first discovery of the U.S. government purchasing and using bulk data to detect i