{"id":2525,"date":"2021-07-24T23:13:30","date_gmt":"2021-07-25T04:13:30","guid":{"rendered":"https:\/\/abudinen.com\/blog\/?p=2525"},"modified":"2021-07-24T23:13:36","modified_gmt":"2021-07-25T04:13:36","slug":"cross-device-tracking","status":"publish","type":"post","link":"https:\/\/abudinen.com\/blog\/2021\/07\/24\/cross-device-tracking\/","title":{"rendered":"Cross-device tracking"},"content":{"rendered":"\n

Cross-device tracking<\/strong> refers to technology which enables the tracking of users across multiple devices such as smartphones, television sets, smart TVs, and personal computers.[1]<\/a><\/sup><\/p>\n\n\n\n

More specifically, cross-device tracking is a technique in which technology companies and advertisers deploy trackers, often in the form of unique identifiers, cookies, or even ultrasonic signals, to generate a profile<\/a> of users across multiple devices, not simply one.[2]<\/a><\/sup> For example, one such form of this tracking uses audio beacons, or inaudible sounds, emitted by one device and recognized through the microphone of the other device.[2]<\/a><\/sup><\/p>\n\n\n\n

This form of tracking is used primarily by technology companies and advertisers who use this information to piece together a cohesive profile of the user.[2]<\/a><\/sup> These profiles inform and predict the type of advertisements<\/a> the user receives.[2]<\/a><\/sup><\/p>\n\n\n\n

Background<\/h2>\n\n\n\n

There are many ways in which online tracking has manifested itself. Historically, when companies wanted to track users’ online behavior, they simply had users sign in to their website.[3]<\/a><\/sup> This is a form of deterministic cross-device tracking, in which the user’s devices are associated with their account credentials, such as their email or username.[4]<\/a><\/sup> Consequently, while the user is logged in, the company can keep a running history of what sites the user has been to and which ads the user interacted with between computers and mobile devices.[4]<\/a><\/sup><\/p>\n\n\n\n

Eventually, cookies<\/a> were deployed by advertisers<\/a>, providing each user with a unique identifier<\/a> in his or her browser so that the user’s preferences can be monitored.[5]<\/a><\/sup> This unique identifier informs the placement of relevant, targeted ads<\/a> the user may receive.[5]<\/a><\/sup> Cookies were also used by companies to improve the user experience, enabling users to pick up where they left off on websites.[6]<\/a><\/sup> However, as users began using multiple devices\u2013\u2013up to around five\u2013\u2013advertisers became confused as to how to track, manage, and consolidate this data across multiple devices as the cookie-based model suggested that each device\u2013\u2013whether a phone, computer, or tablet\u2013\u2013was a different person.[5]<\/a><\/sup><\/p>\n\n\n\n

Other technologies such as supercookies<\/a>, which stay on computers long after the user deletes his or her cookies, and web beacons<\/a>, which are unique images from a URL, are also used by trackers and advertisers to gain increased insight into users’ behavior.[5]<\/a><\/sup> However, advertisers were still limited in that only one device was able to be tracked and associated with a user.[5]<\/a><\/sup><\/p>\n\n\n\n

Thus, cross-device tracking initially emerged as a means of generating a profile of users across multiple devices, not simply one.<\/p>\n\n\n\n

One such tactic for cross-device tracking is called browser fingerprinting<\/a>, and occurs when browsers, which are modifiable to the users’ tastes, produce a unique signal that companies or advertisers can use to single out the user.[5]<\/a><\/sup> Browser fingerprinting has been a cause for concern because of its effectiveness and also since it does not allow for users to opt-out of the tracking.[5]<\/a><\/sup><\/p>\n\n\n\n

Another tactic used by Google is called AdID<\/a> and works on smartphones in tandem with cookies on a user’s computer to track behavior across devices.[3]<\/a><\/sup><\/p>\n\n\n\n

Now, cross-device tracking has evolved into a new, radical form of surveillance technology which enables users to be tracked across multiple devices, including smartphones<\/a>, TVs<\/a>, and personal computers through the use of audio beacons, or inaudible sound, emitted by one device and recognized through the microphone of the other device, usually a smartphone.[2]<\/a><\/sup> In addition, cross-device tracking may presage the future of the Internet of things<\/a> (IoT), in which all types of devices\u2013\u2013such as offices, cars, and homes\u2013\u2013are seamlessly interconnected via the internet.[3]<\/a><\/sup><\/p>\n\n\n\n

Ultrasonic tracking<\/h3>\n\n\n\n

Humans interpret sound by picking up on different frequencies.[2]<\/a><\/sup> Given the variety of sound waves<\/a> that exist, humans can only hear frequencies that are within a certain range\u2013\u2013generally from 20 Hz to 20 kHz. By the age of 30, most humans cannot hear sounds above 18 kHz.[2]<\/a><\/sup><\/p>\n\n\n\n

Ultrasound<\/a>, which is shorter wavelengths greater than or equal to 20 kHz, enables the rapid transmission of data necessary for cross-device tracking to occur.[2]<\/a><\/sup><\/p>\n\n\n\n

Another integral component of cross-device tracking is the usage of audio beacons. Audio beacons are beacons that are embedded into ultrasound, so they cannot be heard by humans.[2]<\/a><\/sup> These audio beacons are used to surreptitiously track a user’s location and monitor online behavior by connecting with the microphone on another device without the user’s awareness.[2]<\/a><\/sup><\/p>\n\n\n\n

In October 2015, the Center for Democracy and Technology<\/a> submitted comments to the Federal Trade Commission<\/a> (FTC) regarding cross-device tracking technology, specifically mentioning SilverPush<\/a>.[7]<\/a><\/sup>[8]<\/a><\/sup><\/p>\n\n\n\n

Audio “beacons” can be embedded into television advertisements. In a similar manner to radio beacons<\/a>, these can be picked up by mobile apps<\/a>.[9]<\/a><\/sup> This allows the behavior of users to be tracked, including which ads were seen by the user and how long they watched an ad before changing the channel.[10]<\/a><\/sup><\/p>\n\n\n\n

In March 2016, the FTC issued warning letters to 12 app developers using cross-device tracking in their apps.[11]<\/a><\/sup> The FTC warned these developers that they may be violating the FTC Act<\/a> if they state or imply that their apps are not tracking television viewing habits when they in fact are.<\/p>\n\n\n\n

Applications<\/h2>\n\n\n\n

Studies have shown that 234 Android<\/a> applications are eavesdropping on these ultrasonic channels without the user’s awareness.[2]<\/a><\/sup><\/p>\n\n\n\n

Applications such as SilverPush<\/a>, Shopkick, and Lisnr are part of an “ultrasonic side-channel” in which the app, often unbeknownst to the user, intercepts ultrasonic signals emitted from the user’s environment, such as from a TV, to track which advertisements the user has heard and how long the person listened to them.[2]<\/a><\/sup><\/p>\n\n\n\n