A few possible sources: - malware on phones (even though apps are supposed to only get anonymous information, there are ways to workaround it. For one a app ca

A few possible sources: - malware on phones (even though apps are supposed to only get anonymous information, there are ways to workaround it. For one a app can just ask your name and many people will put it in.) - cell phone companies selling the data (see for evidence they do this https://www.vice.com/en/article/i-gave-a-bounty-hunter-300-dollars-located-phone-microbilt-zumigo-tmobile/ https://www.vice.com/en/article/i-gave-a-bounty-hunter-300-d...) Bear in mind these companies advertising a capability doesn't mean it works on every target.