Original URL: http://www.theregister.co.uk/2011/05/11/windows_phone_unique_id/

Microsoft stops ID-ing phones in jab at Google

Redmond jettisons unique device identifiers

By Dan Goodin

Posted in Phones, 11th May 2011 19:46 GMT

Microsoft will stop identifying specific mobile devices that use its location-tracking services, a change that differentiates its Windows Phone 7 from Google's competing Android operating system.

Under a new policy, outlined in a letter (PDF) sent to members of Congress on Monday, Microsoft has already stopped storing and using unique identifiers collected from devices that use Windows location services to pinpoint nearby coffee shops or get driving directions. What's more, devices running a forthcoming Windows update will no longer send the identifiers to the company's location service at all.

“We believe that, when designed, deployed and managed responsibly, the location-based feature of a mobile operating system should function as a tool for the user and the applications he or she elects to use, and not as a means to generate a database of sensitive information that can enable a party to surreptitiously 'track' a user,” Andy Lees, president of Microsoft's mobile communications business, wrote. “Without a unique identifier, or some other significant change to our operating system or practices, we cannot track an individual device.”

Lees made many of the same points in a recent blog post.

The change comes as Congress and privacy advocates scrutinize similar location services offered by phones running Google and Apple OSes. As previously reported, when Android phones have location services enabled, they collect the MAC address, signal strength and GPS coordinates of every wireless network they see and zap it to Google servers, along with the unique ID of the handset.

Android handsets also send a unique ID when transmitting cell tower information. These events happen several times an hour, according to independent researcher Samy Kamkar.

By combining the locations and the unique identifier collected several times a day every single day, it wouldn't be hard for Google – or someone subpoenaing Google – to figure out where a user lives and works. And since Android phones track the signal strength of each Wi-Fi network they see, there's a good chance the data could be used to learn the MAC address of a user's home and business routers.

Microsoft, Google, and Apple phones all store the locations of nearby Wi-Fi networks and cell towers so that location services consume less battery power and work in areas where satellite signals aren't available. Much of the recent hoopla over location services started last month, when researchers disclosed that iPhones often stored a “scary” amount of this data and allowed it to be transferred unencrypted to users' computers. Apple eventually changed this practice.

Apple has said the file is compiled only when location services are enabled on the iPhone, but Kamkar has said the locations were stored even when the service was turned off.

For Google's part, the locations of Wi-Fi and cell towers are cached by Android phones only when location services are turned on, and data is regularly deleted to prevent it from storing too large a list. The company has said it anonymizes the location data it collects.

But so far Google has showed no signs that it plans to curb the collection of unique identifiers, making it the only one of the three mobile OS providers to do so, Kamkar said. ®

Update

A Google spokeswoman emailed us to say that it's not accurate to say the company collects a "unique identifier" from phones that share location data with the company. She cited written testimony submitted this week to Congress that states the following:

Google is also very careful about how we use and store the data that is generated by location-based services. The location information sent to Google servers when users opt in to location services on Android is anonymized and stored in the aggregate and is not tied or traceable to a specific user. The collected information is stored with a hashed version of an anonymous token, which is deleted after approximately one week.