China’s internet censorship has been the topic of discussion among marketers for some time. Now a cybersecurity company has discovered more than 66,000 rules controlling content for search engines and media sites operating in the country. It may be doing more harm than good for search engines outside of China, according to the report.

Citizen Lab, a cybersecurity research group at the University of Toronto, analyzed eight popular search platforms operating in China. Companies analyzed included the three search engines Baidu, Sogou, and Microsoft Bing as well as four Chinese social media networks including Weibo, a microblogging site similar to Twitter; Douyin, the Chinese version of Tiktok; Bilibili, a video-sharing platform similar to YouTube; and Baidu Zhidao, a question-and-answer site similar to Quora. The firm also tested Jingdong, a Chinese e-commerce platform similar to Amazon.

Microsoft Bing is the only search platform analyzed that was not operated by a Chinese company.

The search engines, including Bing, have created algorithms to “hard-censor” queries deemed politically sensitive by returning no results or by limiting results to select sources, mostly government agencies. On web search engines operating in China, “soft-censored” queries will generally only show results from Chinese government websites and state-aligned media. On social media sites, soft-censored queries will only serve-up results from accounts that have a certain level of approval and verification.

Many of the censorship rules target politically sensitive material like references to Chinese political figures such as Xi Jinping, banned religious movements like Falun Gong, and major historical events like 1989 Tiananmen Square protests. Other rules targeted activities such as gambling, drug use, pornography, and the buying and selling of weapons.

Citizen Lab’s method of measuring search censorship requires testing large swaths of text for content-triggering censorship and, if present, isolating the triggers censored.

The company also uses special search queries it calls “truisms” to wrap search strings, so they either have a large number of results, if not censored, or zero results if they are censored.

The truisms work by using advanced search operators that search platforms support. As an example, many search platforms support searching for results that contain either one string or another. Thus, instead of “xi jinping”, you might create a truism by searching for “xi jinping | the,” where the “|” symbol means “or.”

All search platforms have some form of content moderation. Google, for example, might delist single web pages or websites that contain content that is illegal to access in a specific country or region.

But the search engines analyzed that operate in China, including Microsoft Bing, used broad, keyword-based censorship rules to restrict queries for certain types of content to only show results from Chinese government websites and state-aligned media — or even censoring all results for a query altogether.

Baidu has more censorship rules than Bing, but Bing’s political censorship rules were broader and affected more search results than Baidu. Bing also restricted displaying search results from a greater number of website domains.

The research shows that rather than North American companies having a positive influence on the Chinese market, the Chinese market may be having a negative influence on these companies, according to Citizen Lab. Previous work has shown how the Chinese censorship systems designed by Microsoft and Apple have affected users outside of China.