In brief: It’s no secret that mobile apps harvest user data and share it with other companies, but the true extent of this practice may come as a surprise. In a new study carried out by researchers from Oxford University, it’s revealed that almost 90 percent of free apps on the Google Play store share data with Alphabet.

The researchers, who analyzed 959,000 apps from the US and UK Google Play stores, said data harvesting and sharing by mobile apps was now “out of control.”

“We find that most apps contain third party tracking, and the distribution of trackers is long-tailed with several highly dominant trackers accounting for a large portion of the coverage,” reads the report.

It’s revealed that most of the apps, 88.4 percent, could share data with companies owned by Google parent Alphabet. Next came a firm that’s no stranger to data sharing controversies, Facebook (42.5 percent), followed by Twitter (33.8 percent), Verizon (26.27 percent), Microsoft (22.75 percent), and Amazon (17.91 percent).

According to The Financial Times, which first reported the research, information shared by these third-party apps can include age, gender, location, and information about a user’s other installed apps. The data "enables construction of detailed profiles about individuals, which could include inferences about shopping habits, socio-economic class or likely political opinions."

Big firms then use the data for a variety of purposes, such as credit scoring and for targeting political messages, but its main use is often ad targeting. Not surprising, given that revenue from online advertising is now over $59 billion per year.

According to the research, the average app transfers data to five tracker companies, which pass the data on to larger firms. The biggest culprits are news apps and those aimed at children, both of which tend to have the most third-party trackers associated with them.

The problem, according to project lead Reuben Binns, is due to most apps being free and relying on advertising to make money. As such, data sharing has become rampant.

Responding to the report, Google said: "Across Google and in Google Play we have clear policies and guidelines for how developers and third-party apps can handle data and we require developers to be transparent and ask for user permission. If an app violates our policies, we take action."

The tech giant also suggests that the study is misleading. "We disagree with the methodology and the findings of this study. It mischaracterises ordinary functional services like crash reporting and analytics, and how apps share data to deliver those services."

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