Cross-Device Tracking: a privacy invasive tracking method
Marketing companies are always on the lookout for new methods to track user activity on the Internet. These information are used to display targeted advertisement to users which have a better return than less-targeted ads.
The more a company knows about a user, the higher the return and that is the main reason why companies step up the tracking game despite public outcry about it and the rise of ad-blockers.
In fact, tracking is one of the core reasons -- the other is invasive ads -- that users install ad-blockers on their devices.
Cross-Device Tracking is yet another ingenious method to track users. As the name suggests, it has the capability to track users across devices. This is done by using high-frequency sounds that are inaudible to the human ear.
The method links devices such as web browsers, mobile devices or TVs through the use of these sounds and browser cookies resulting in a combined tracking profile of the user across devices instead of just individual devices.
The technique allows companies to track users even more, as they know for instance for how long TV ads are watched.
SilverPush, one of the companies that uses cross-device tracking, monitors 18 million smartphones already as of April 2015.
For those who are tracked, it is nearly impossible to tell if they are. These companies don't offer opt-outs and there is no software available that blocks the transmission of high-frequency audio signals. Furthermore, it is unclear which apps, ads or companies make use of the technology. The technique is limited by distance first and foremost.
It seems as well that only apps are used currently to pick up these audio signals, and that ads on the PC and TVs are merely used to push out these signals.
The CDT letter of SilverPush revealed some information, including that the company's software is used on 67 apps, and that "more than a dozen marketing companies" use cross-device tracking.
One recourse that users have is to limit microphone access on their mobile devices. The main issue here is that this is not available by default on many devices. While there are apps available that block the microphone altogether, they may cause usability issues as the microphone needs to be enabled for phone calls for instance.
It is interesting to note that Cross-Device Tracking resembles badBios, a malware discovered in 2013 that uses inaudible sounds to bridge air-gapped computer systems. (via Ars Technica)

Doesn’t Windows 8 know that www. or http:// are passe ?
Well it is a bit difficulty to distinguish between name.com domains and files for instance.
I know a service made by google that is similar to Google bookmarks.
http://www.google.com/saved
@Ashwin–Thankful you delighted my comment; who knows how many “gamers” would have disagreed!
@Martin
The comments section under this very article (3 comments) is identical to the comments section found under the following article:
https://www.ghacks.net/2023/08/15/netflix-is-testing-game-streaming-on-tvs-and-computers/
Not sure what the issue is, but have seen this issue under some other articles recently but did not report it back then.
Omg a badge!!!
Some tangible reward lmao.
It sucks that redditors are going to love the fuck out of it too.
With the cloud, there is no such thing as unlimited storage or privacy. Stop relying on these tech scums. Purchase your own hardware and develop your own solutions.
This is a certified reddit cringe moment. Hilarious how the article’s author tries to dress it up like it’s anything more than a png for doing the reddit corporation’s moderation work for free (or for bribes from companies and political groups)
Almost al unlmited services have a real limit.
And this comment is written on the dropbox article from August 25, 2023.
First comment > @ilev said on August 4, 2012 at 7:53 pm
For the God’s sake, fix the comments soon please! :[
Yes. Please. Fix the comments.
With Google Chrome, it’s only been 1,500 for some time now.
Anyone who wants to force me in such a way into buying something that I can get elsewhere for free will certainly never see a single dime from my side. I don’t even know how stupid their marketing department is to impose these limits on users instead of offering a valuable product to the paying faction. But they don’t. Even if you pay, you get something that is also available for free elsewhere.
The algorithm has also become less and less savvy in terms of e.g. English/German translations. It used to be that the bot could sort of sense what you were trying to say and put it into different colloquialisms, which was even fun because it was like, “I know what you’re trying to say here, how about…” Now it’s in parts too stupid to translate the simplest sentences correctly, and the suggestions it makes are at times as moronic as those made by Google Translations.
If this is a deep-learning AI that learns from users’ translations and the phrases they choose most often – which, by the way, is a valuable, moneys worthwhile contribution of every free user to this project: They invest their time and texts, thereby providing the necessary data for the AI to do the thing as nicely as they brag about it in the first place – alas, the more unprofessional users discovered the translator, the worse the language of this deep-learning bot has become, the greater the aggregate of linguistically illiterate users has become, and the worse the language of this deep-learning bot has become, as it now learns the drivel of every Tom, Dick and Harry out there, which is why I now get their Mickey Mouse language as suggestions: the inane language of people who can barely spell the alphabet, it seems.
And as a thank you for our time and effort in helping them and their AI learn, they’ve lowered the limit from what was once 5,000 to now 1,500…? A big “fuck off” from here for that! Not a brass farthing from me for this attitude and behaviour, not in a hundred years.