In a study published online Monday in the journal Proceedings of the National Academy of Sciences, Stanford University researchers demonstrated how they used publicly available sources—like Google searches and the paid background-check service Intelius—to identify “the overwhelming majority” of their 823 volunteers based only on their anonymized call and SMS metadata.

Using data collected through a special Android app, the Stanford researchers determined that they could easily identify people based on their call and message logs.

The results cast doubt on claims by senior intelligence officials that telephone and Internet “metadata”—information about communications, but not the content of those communications—should be subjected to a lower privacy threshold because it is less sensitive.

Contrary to those claims, the researchers wrote, “telephone metadata is densely interconnected, susceptible to reidentification, and enables highly sensitive inferences.” Study shows phone metadata is much more sensitive than top spies admit