Although the "Cell ID", or mast location, data sent to Google was encrypted and the company said it had considered using it only to improve messaging services, criminal hackers could potentially intercept it and track users' movements.
According to Quartz, phones running on Google's Android OS have been collecting addresses of nearby cellular towers - even when location-tracking services are turned off - and sending that data back to Google.
According to a Google spokesperson, the data was not used or stored, and that the company was taking steps to stop the practice by the end of November. Those addresses were included in information, such as Cell ID codes, sent to Google for almost a year.
Cell ID codes - data exchanged between a smartphone and a cell tower - can be used to determine roughly where a mobile device is located.
Report claimed, this practice was not used to enhance the ad-serving system, but rather to improve what Google calls its "heartbeat system", which ensures that the Android Phones remain connected and users get their messages properly and quickly. That was not the case with the Cell ID collection, whether or not the data was stored by Google.
This means that even people who actively turn off their Global Positioning System tracking service - thinking their locations will no longer be shared - were being tracked by Google nonetheless. The reports mean that recently tower information transmitted by Android smartphones has been sent in real time to Google's servers. "However, we never incorporated Cell ID into our network sync system, so that data was immediately discarded, and we updated it to no longer request Cell ID".
"It has pretty concerning implications", said Bill Budington, a software engineer who works for the Electronic Frontier Foundation, a nonprofit organization that advocates for digital privacy.
"It seems quite intrusive for Google to be collecting such information that is only relevant to carrier networks when there are no SIM card or enabled services", Matthew Hickey, a security expert and researcher, told media in London.
Phone networks routinely collect data about where mobile users are, via information recorded from phone masts across the country.
Android phones dominate the global market.