These Android apps have been tracking you, even when you say stop

[NcoII]

Some apps may track your activity over time, even when you tell them to forget the past. And there's nothing you can do about it.

Roughly 17,000 Android apps collect identifying information that creates a permanent record of the activity on your device, according to research from the International Computer Science Institute that was shared with CNET. The data collection appears to violate the search giant's policy on collecting data that can be used to target users for advertising in most cases, the researchers said.

The apps can track you by linking your Advertising ID -- a unique but resettable number used to tailor advertising -- with other identifiers on your phone that are difficult or impossible to change. Those IDs are the device's unique signatures: the MAC address, IMEI and Android ID. Less than a third of the apps that collect identifiers take only the Advertising ID, as recommended by Google's best practices for developers.

"Privacy disappears" when apps collect those persistent identifiers, said Serge Egelman, who led the research. He said his team, which reported the findings to Google in September, observed most of the apps sending identifying information to advertising services, an apparent violation of Google's policies. 

The company's policies allow developers to collect the identifiers but forbid them from combining the Advertising ID with hardware IDs without explicit consent of the user, or from using the identifiers that can't be reset, to target ads. What's more, Google's best practices for developers recommend collecting only the Advertising ID.

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