Your Phone Knows You’re at the Doctor, and Data Brokers Do, Too — Then Profit From It

Chris McQueen finished treatment for leukemia a year and a half ago, but the ads for fake cures never stopped. Juice cleanses to cure cancer, “natural” cancer treatments, clinics in Mexico promising full recovery with little chemotherapy — all appeared on McQueen’s mobile phone during routine oncologist visits and monthly bloodwork. McQueen and others have taken to social media to vent about companies known as data brokers tracking their whereabouts via their smartphones’ location data, connecting it with other data gathered about them, and then drawing inferences about their health struggles to sell to companies hawking unproven treatments. “It makes me feel sick to my stomach,” said McQueen, who lives in San Diego and fears some patients are putting themselves at risk, potentially fatally, if they try such untested treatments instead of following their oncologists’ advice. More than 92% of patients in a 2022 American Medical Association survey said they believed their health data should not be available for purchase. But many people might not realize that when they are sitting in a hospital, an abortion clinic, or an Alcoholics Anonymous meeting in a church basement, the location...