Free Expression Online
Studies of Internet filtering, network interference, and other technologies and practices that impact freedom of expression online.
Featured in Free Expression Online
This document provides a high-level introduction to deep packet inspection, Internet filtering, and targeted intrusion dual-use technologies with the aim of familizaring the reader with their key technical features, the surrounding international human rights law framework, and some of the leading research to date on their deployment.
In this work, we study how Tencent implements image filtering on WeChat. We found that Tencent implements realtime, automatic censorship of chat images on WeChat based on what text is in an image and based on an image’s visual similarity to those on a blacklist. Tencent facilitates this realtime filtering by maintaining a hash index of MD5 hashes of sensitive image files.