Almost 17,000 apps were found to be transmitting persistent identifiers which can be used to track users and are prohibited by both Google and GDPR without users consent.
A research carried out by AppCensur determined that out of 24,000 apps in its database that could send the Advertising ID, a unique identifier created by Google, which is legally used by Google and other companies to served contextual ads.
However, more than 2/3rd of the apps were also found to be sending other unique identifiers, like Android ID, IMEI number, among others, which are not allowed by Google. This was done without users’ consent making if illegal in most countries.
Two of these apps were downloaded over a billion times, another three were downloaded half-a-billion times and several others have download count of more than 100 million.
Some of the prominent names included in the list of offenders are Subway Surfers, a popular running game, Flipboard – a Microsoft backed news app, Talking Tom – a wildly popular childrens app, and Clean Master – a Antivirus and cleaner app that is downloaded more than 1 billion times.
The research group at AppCensus tested these apps with data and found most of these apps were sending the data to companies involved in several mobile advertising, the researchers think that the companies are using to either track users or place advertisements.
List of Top 20 apps unlawfully tracking users
| App Name | Installs | Data Types | Recipient |
| Clean Master – Antivirus, Cleaner & Booster | 1B | Ad ID + Android ID | t.appsflyer.com |
| Subway Surfers | 1B | Android ID | api.vungle.com |
| Flipboard: News For Our Time | 500M | Ad ID + Android ID | ad.flipboard.com |
| My Talking Tom | 500M | Ad ID + Android ID | m2m1.inner-active.mobi |
| Temple Run 2 | 500M | Ad ID + Android ID | live.chartboost.com |
| 3D Bowling | 100M | Ad ID + Android ID + IMEI | ws.tapjoyads.com |
| 8 Ball Pool | 100M | Ad ID + Android ID | ws.tapjoyads.com |
| Agar.io | 100M | Ad ID + Android ID | ws.tapjoyads.com |
| Angry Birds Classic | 100M | Android ID | ads.api.vungle.com |
| Audiobooks from Audible | 100M | Ad ID + Android ID | api.branch.io |
| Azar | 100M | Ad ID + Android ID | api.branch.io |
| B612 – Beauty & Filter Camera | 100M | Ad ID + Android ID | t.appsflyer.com |
| Banana Kong | 100M | Ad ID + Android ID | live.chartboost.com |
| Battery Doctor – Battery Life Saver & Battery Cooler | 100M | Ad ID + Android ID + IMEI | t.appsflyer.com |
| BeautyPlus – Easy Photo Editor & Selfie Camera | 100M | Ad ID + Android ID | t.appsflyer.com, live.chartboost.com |
| Bus Rush | 100M | Ad ID + Android ID | ads.api.vungle.com, ws.tapjoyads.com |
| CamScanner – Phone PDF Creator | 100M | Ad ID + Android ID + IMEI | t.appsflyer.com |
| Cheetah Keyboard – Emoji & Stickers Keyboard | 100M | Ad ID + Android ID | t.appsflyer.com |
| Cooking Fever | 100M | Ad ID + Android ID | ws.tapjoyads.com |
| Cut The Rope Full FREE | 100M | Ad ID + Android ID | ws.tapjoyads.com |
Source: AppCensus Blog
