Gillette knows whether you shave because Tinder told it about you

Lately on Spark we've been talking a lot about how our phones track us and seem, sometimes, to know more about us than we do. Just recently,  Google was caught out recording the movements of Android phone users even when they had deliberately opted out by disabling location tracking on their phones.

But it turns out the big tech companies like Google aren't the only ones acting like Big Brother. There are a whole bunch of little brothers, too. And they may be more a lot more insidious than Google or Facebook.

Sean O'Brien, a visiting fellow at the Yale University Privacy Lab, just published a disturbing report that shows that nearly every popular app -- and a lot of much smaller apps too -- contain hidden third-party trackers. A single app can contain dozens of these trackers, and you don't even know they're there.

"We're talking Tinder, Uber, Snapchat, Spotify," he says.

"From the sample that we looked at, which was only 300 apps, we found a little over 75 per cent, so that's quite a lot. As we keep looking, and we've now looked at about 500 apps, the number is not going down."

Sean says this is leading us towards a future like that shown in the film Minority Report, where advertisements in malls and on streets address people individually, by name. "It could happen," he says.

Mostly, the tracking apps are collecting our location data, which is granular enough that some can figure out where we live, where our family lives, and where we work. One tracker in particular can do this by sending out tones at subsonic frequencies, which are picked up by our phone's microphone, which then relays its position - right down to the aisle we might be perusing in a particular store.

Others are even more invasive, reporting users' names, dates of birth, and so on, Sean says. This is especially disturbing because the trackers are often found in pregnancy and baby apps, as well as general health apps.

"That could have serious implications for people well down the road," he says.

Although they only tested Android phones, Sean believes the same trackers are also in the equivalent iPhone apps, as well as Windows phones and even computers.

There isn't much consumers can do, besides avoid using those apps. But some, like Google's native apps, are difficult to delete from phones. As an alternative, he recommends sites like F-Droid, which features a catalogue of apps that are not part of the Google Play store ecosystem, and are free and open source.

He says government regulation may ultimately be necessary to curtail such an invasive, and opaque, practice.

"Ultimately, we need more transparency."