Test requests for Wi-Fi connection allow you to track users


A team of specialists from the University of Hamburg demonstrated how Wi-Fi connection verification requests can be used to identify and track devices and, accordingly, their owners.

Mobile devices transmit connection verification requests in order to get information about the nearest Wi-Fi networks and establish a connection. The access point that receives such a request sends a response, thereby establishing a connection between the two devices.

According to the researchers, test requests may contain information identifying the owner of the device, depending on how old it is and on the basis of which OS it works. For example, they may contain a list of preferred networks with SSIDs. As the experts explained, 23% of test requests contain the SSID IDs of the networks to which the device was connected before.

During the experiment, the researchers intercepted a large number of connection verification requests and analyzed the types of data transmitted to them without the knowledge of users. In total, they intercepted 252242 requests, of which 116961 requests (46.4%) in the 2.4GHz band. 28,836 requests (24.7%) contained at least one SSID. In the 5 GHz band, experts recorded 135281 requests (53.6%), of which 29,653 requests (21.9%) contained SSIDs.

“We assume that many SSIDs come from users trying to set up a network connection manually. They enter the SSID and password through advanced network settings, and, apparently, mistakenly enter the wrong strings as the SSID,” the researchers noted.

A small but significant number of test requests containing SSIDs potentially pass passwords to the SSID field.

“We found that 11.8% of the transmitted test requests contain numeric strings with 16 or more digits, which are probably the initial passwords of popular German home routers (for example, FritzBox or Telekom),” the researchers said in the report.

The SSIDs also included strings corresponding to the stores’ Wi-Fi networks. The experts identified 106 different names and/or surnames, three email addresses and 92 different houses previously added as trusted networks.

As the researchers explained, randomization of MAC addresses will help prevent user tracking.

“The newer the device and its OS, the more information is skipped, and the fields are randomized. At the same time, various studies still describe how even modern devices can be tracked thanks to other information contained in them,” the authors of the study reported.

Experts recommend that users delete SSIDs that they no longer use, disable automatic network connectivity, and disable connection verification requests. This latter measure has some disadvantages, including an increase in battery consumption and an increase in connection time.

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