Pierluigi Paganini
November 21, 2015
A few days ago, the Center for Democracy and Technology (CDT) warned that the Indian company SilverPush has developed a technology that allows adverts to ping inaudible commands to mobile devices.
“Millions of mobile devices with SilverPush powered SDK are constantly listening to SilverPush patented audio beacons (ultrasonic) which are watermarked in Televison ad commercial. A pair is made once a SDK comes in proximity of audio beacon. The individual ID is mapped back to its audience genome and a brand-consumer journey has been started.” states the official description provided by SilverPush.
An application that implements the SilverPush technology car gather these near-ultrasonic messages by using the mobile microphone and then send data and mobile information (i.e. IMEI number, location, operating system version, and potentially the identity of the owner) to a server elsewhere.
The application has a significant impact on the user’s privacy but represents a powerful instrument for the advertising industry. When the owner of a mobile device watches any advert embedding the SilverPush ultrasonic messages, his data are collected and sent back to a remote server.
A research has identified 30 applications using the SilverPush SDK, including shopping apps developed by companies in India and Far East.
Is it legal? Does the technology require the user’s consent?
“This kind of technology is fundamentally surreptitious in that it doesn’t require consent; if it did require it then the number of users would drop,” Joe Hall, chief technologist at CDT told The Register on Thursday. “It lacks the ability to have consumers say that they don’t want this and not be associated by the software.”
Another disconcerting aspect of the technology that the most applications that implement the SilverPush doesn’t notify it to the end-users.
In US and Europe end-user must explicitly give its consent, in Europe and in the US the exploitation of this kind of technology is not legal.
Imagine any abuse of the SilverPush technology by a repressive regime, the technology could allow a rogue government to track the mobile devices used by the dissidents.
How does it work?
The researcher Kevin Finisterre from Digital Munition firm analyzed the code of the SilverPush and has published his the results of the research on the GitHub.
The technology assigns letters of the alphabet to high-pitch tones (i.e. The letter ‘A’ is coded with a 18kHz tone, and 19.125kHz is a ‘P’). The combination of letters is used to identify TV ads, for example the ‘AP’ is associated to a Geico ad and display an image and link to the insurance biz.
Finisterre also demonstrated that is possible to spoof the sounds or interfere with the technology by generating randomly ultrasonic tones.
(Security Affairs – SilverPush, privacy)
Hacking / September 25, 2025
