Researchers in Canada, the U.S., and Australia teamed up for the study, published Wednesday in the BMJ. They tested 24 popular health-related apps used by patients and doctors in those three countries on an Android smartphone (the Google Pixel 1). Among the more popular apps were medical reference site Medscape, symptom-checker Ada, and the drug guide Drugs.com. Some of the apps reminded users when to take their prescriptions, while others provided information on drugs or symptoms of illness.
They then created four fake profiles that used each of the apps as intended. To establish a baseline of where network traffic related to user data was relayed during the use of the app, they used each app 14 times with the same profile information. Then, prior to the 15th use, they made a subtle change to this user information. On this final use, they looked for differences in network traffic, which would indicate that user data obtained by the app was being shared with third parties, and where exactly it was going to.
Overall, they found 79 percent of apps, including the three listed above, shared at least some user data outside of the app itself. While some of the unique entities that had access to the data used it to improve the app’s functions, like maintaining the cloud where data could be uploaded by users or handling error reports, others were likely using it to create tailored advertisements for other companies. When looking at these third parties, the researchers also found that many marketed their ability to bundle together user data and share it with fourth-party companies even further removed from the health industry, such as credit reporting agencies. And while this data is said to be made completely anonymous and de-identified, the authors found that certain companies were given enough data to easily piece together the identity of users if they wanted to.