TechCrunch reports: Onavo Protect, the VPN client from the data-security app maker acquired by Facebook back in 2013, has now popped up in the Facebook app itself, under the banner "Protect" in the navigation menu. Clicking through on "Protect" will redirect Facebook users to the "Onavo Protect -- VPN Security" app's listing on the App Store. We're currently seeing this option on iOS only, which may indicate it's more of a test than a full rollout here in the U.S. Marketing Onavo within Facebook itself could lead to a boost in users for the VPN app, which promises to warn users of malicious websites and keep information secure as you browse. But Facebook didn't buy Onavo for its security protections. Instead, Onavo's VPN allow Facebook to monitor user activity across apps, giving Facebook a big advantage in terms of spotting new trends across the larger mobile ecosystem. 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. Further reading: Do Not, I Repeat, Do Not Download Onavo, Facebook's Vampiric VPN Service (Gizmodo).