Metadata that is generated through phone calls discloses a significant amount of personal information, a new study from Stanford University in the US has found.

The paper, which was published in the Proceedings of the National Academy of Sciences, revealed that information that is logged, such as the length and time of a phone call, can be used to generate accurate profiles of people.

Analyzing more than 800 smartphone logs, which were made up of 250,000 calls and 1.2 million texts, two researchers at the university were able “infer” a lot about a person.

For example, it is reasonable to deduce that an individual who makes a call to a pharmacy/drugstore, a cardiologist and cardiac arrhythmia monitoring device hotline, is likely to be suffering from “cardiac arrhythmia”.

“I was somewhat surprised by how successfully we inferred sensitive details about individuals."

“I was somewhat surprised by how successfully we inferred sensitive details about individuals,” commented Patrick Mutchler, a graduate student at Stanford and co-author of the report.

“It feels intuitive that the businesses you call say something about yourself. But when you look at how effectively we were able to identify that a person likely had a medical condition, which we consider intensely private, that was interesting.”

These findings have huge security and privacy implications, as presently, in the US, government agencies are able to access this information without the need for a warrant.

Interestingly, the authors of the paper, which also included Jonathan Mayer and John C. Mitchell, noted that some officials probably consider this collection of data to be “trivial”.

In other words, they don’t see it as being intrusive. However, as this study demonstrates, the metadata is sensitive and revealing.

“The results of our study are unambiguous: there are significant privacy impacts associated with telephone metadata surveillance,” the authors of the paper highlighted.

“Telephone metadata is densely interconnected, easily reidentifiable, and trivially gives rise to location, relationship, and sensitive inferences.”