Facebook Inc. has started pushing a virtual private network app to some users, but it might be best to Mark Zuckerberg bearing gifts.

The Onavo VPN app, acquired by Facebook in 2013, is being offered as an option to iOS users under the name of “Protect” in the app menu within Facebook. Once users click on the option, they are taken to the Apple App Store to download the “Onavo Protect – Internet Security” app.

Virtual private networks work by tunneling traffic through a third-party server and can be used to bypass geographic restrictions or for privacy reasons, such as masking an IP address and preventing traffic from being monitored by internet service providers. The Onava app does indeed meet the definition of a VPN, but the trojan horse of the story is that all the data running through the app is being used by Facebook to monitor every single thing a user does.

“Onavo’s VPN allows Facebook to monitor user activity across apps, giving Facebook a big advantage in terms of spotting new trends across the larger mobile ecosystem,” TechCrunch explained Monday. “For example, Facebook gets an early heads up about apps that are becoming breakout hits; it can tell which are seeing slowing user growth; it sees which apps’ new features appear to be resonating with their users, and much more.”

TechCrunch pointed to a Wall Street Journal piece from August that noted Facebook has already used data gathered by the Onavo app “most notably in its battle with Snapchat.” Facebook used the data to identify that Instagram’s Stories feature was slowing Snapchat user growth before Snap Inc. itself admitted to the fact. The social network giant at the time said the disclosure for Onavo was clear.

Indeed, Facebook is not shy in admitting the data-gathering, even if it’s not shouting about it. The disclosure on the app notes that “Onavo collects your mobile data traffic. This helps us improve and operate the Onavo service by analyzing your use of websites, apps, and data. Because we’re part of Facebook, we also use this info to improve Facebook products and services, gain insights into the products and services people value, and build better experiences.”

VPNs can and do serve a useful purpose, but Facebook is not the first VPN provider to be accused of spying on users and it likely won’t be the last. Popular VPN provider Hotspot Shield was accused of injecting its own advertising into web pages in a Federal Trade Commission complaint in August.

Picture: QuartierLatin1968/Flickr