China’s surveillance of its citizens’ digital activities is common knowledge. However, questions remain concerning what content is targeted by government censors and how these blacklists change in response to current events.

A new study released this month in First Monday uncovers more than 4,000 unique keywords censored over the last year and a half on Chinese instant messaging platforms. Focusing on Skype and the microblogging service Sina Weibo, the researchers cultivated their keyword list using reverse-engineering techniques such as packet sniffing, which captures and analyzes packets of data as they pass through a network.

More than 20% of the terms targeted on Sina Weibo, it turns out, related to technology, including specific URLs, spyware, and technical terms.