Two Stanford grad students conducted a research project to find out what kind of actual data can be derived from mobile phone metadata:
Two Stanford computer science students were able to acquire detailed information about people’s lives just from telephone metadata — the phone number of the caller and recipient, the particular serial number of the phones involved, the time and duration of calls and possibly the location of each person when the call occurred.
The researchers did not do any illegal snooping — they worked with the phone records of 546 volunteers, matching phone numbers against the public Yelp and Google Places directories to see who was being called.
From the phone numbers, it was possible to determine that 57 percent of the volunteers made at least one medical call. Forty percent made a call related to financial services.
The volunteers called 33,688 unique numbers; 6,107 of those numbers, or 18 percent, were isolated to a particular identity.
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They crowdsourced the data using an Android application and conducted an analysis of individual calls made by the volunteers to sensitive numbers, connecting the patterns of calls to emphasize the detail available in telephone metadata, Mayer said.
“A pattern of calls will, of course, reveal more than individual call records,” he said. “In our analysis, we identified a number of patterns that were highly indicative of sensitive activities or traits.”
For example, one participant called several local neurology groups, a specialty pharmacy, a rare-condition management service, and a pharmaceutical hotline used for multiple sclerosis.
Another contacted a home improvement store, locksmiths, a hydroponics dealer and a head shop.
The researchers initially shared the same hypothesis as their computer science colleagues, Mayer said. They did not anticipate finding much evidence one way or the other.
“We were wrong. Phone metadata is unambiguously sensitive, even over a small sample and short time window. We were able to infer medical conditions, firearm ownership and more, using solely phone metadata,” he said.
