The Web’s sixth sense: A study of scripts accessing smartphone sensors

Anupam Das, Nikita Borisov, Gunes Acar, Amogh Pradeep

Research output: Chapter in Book/Report/Conference proceedingConference contribution


We present the first large-scale measurement of smartphone sensor API usage and stateless tracking on the mobile web. We extend the OpenWPM web privacy measurement tool to develop OpenWPM-Mobile, adding the ability to emulate plausible sensor values for different smartphone sensors such as motion, orientation, proximity and light. Using OpenWPM-Mobile we find that one or more sensor APIs are accessed on 3 695 of the top 100K websites by scripts originating from 603 distinct domains. We also detect fingerprinting attempts on mobile platforms, using techniques previously applied in the desktop setting. We find significant overlap between fingerprinting scripts and scripts accessing sensor data. For example, 63% of the scripts that access motion sensors also engage in browser fingerprinting. To better understand the real-world uses of sensor APIs, we cluster JavaScript programs that access device sensors and then perform automated code comparison and manual analysis. We find a significant disparity between the actual and intended use cases of device sensor as drafted by W3C. While some scripts access sensor data to enhance user experience, such as orientation detection and gesture recognition, tracking and analytics are the most common use cases among the scripts we analyzed. We automated the detection of sensor data exfiltration and observed that the raw readings are frequently sent to remote servers for further analysis. Finally, we evaluate available countermeasures against the misuse of sensor APIs. We find that popular tracking protection lists such as EasyList and Disconnect commonly fail to block most tracking scripts that misuse sensors. Studying nine popular mobile browsers we find that even privacy-focused browsers, such as Brave and Firefox Focus, fail to implement mitigations suggested by W3C, which includes limiting sensor access from insecure contexts and cross-origin iframes. We have reported these issues to the browser vendors.

Original languageEnglish (US)
Title of host publicationCCS 2018 - Proceedings of the 2018 ACM SIGSAC Conference on Computer and Communications Security
PublisherAssociation for Computing Machinery
Number of pages18
ISBN (Electronic)9781450356930
StatePublished - Oct 15 2018
Event25th ACM Conference on Computer and Communications Security, CCS 2018 - Toronto, Canada
Duration: Oct 15 2018 → …

Publication series

NameProceedings of the ACM Conference on Computer and Communications Security
ISSN (Print)1543-7221


Other25th ACM Conference on Computer and Communications Security, CCS 2018
Period10/15/18 → …


  • Fingerprinting
  • Mobile browser
  • On-line tracking
  • Sensors

ASJC Scopus subject areas

  • Software
  • Computer Networks and Communications


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