NHK has learned that personal information has unintentionally been made publicly available on a service operated by Google.



Google Groups is a free service that allows people to create a group to share files after appointing a group member as the administrator.



The service started in the 2000s, but NHK found out this year that emails shared among users of certain groups, such as those set up by private businesses, labor unions and medical institutions, could be accessed by anyone on the web.



The groups included the Japan Airlines labor union and a public medical institution in Osaka City.



In the case of the JAL labor union, the names and mobile phone numbers of more than 2,500 members could be viewed by outsiders. At the Osaka medical institution, patients' symptoms and other medical information were also publicly accessible.



The settings for these sites have now been changed to make them private.



Previously, the service's default setting allowed any web user to access information. But Google changed the default setting to private after it came to light in 2013 that emails of Japanese government officials could be viewed by anyone.



Despite the change, many Google Groups can still be accessed by outsiders. It is believed the administrators of these groups mistakenly chose the setting that allows any web user to view the data.



Some users told NHK they did not know that information could be accessed by outsiders depending on the settings.



Google told NHK that its product is designed to allow its users to manage their data. The company recommends that group administrators review and adjust the settings if necessary.



Ritsumeikan University Professor Uehara Tetsutaro, an expert on information security, urges people to be cautious when they use a free service. He says users should check that information meant for internal use cannot be accessed by outsiders.