Chinese law enforcement may be behind a disinformation operation that’s been trying to spread propaganda across dozens of social networks, according to Facebook’s parent Meta.

The operation, dubbed “Spamouflage,” has been spotted on over 50 social media platforms, including Facebook, Instagram, TikTok, Twitter, and Reddit, the company said in research published on Tuesday.

The covert op has targeted users in the US, Taiwan, UK, Australia, and Japan with positive commentary about China, including the country’s Xinjiang region, all the while criticizing Western foreign policies. At one point, the operation tried to promote a conspiracy theory that COVID-19 originated in the US.

In addition, the group has been posting pro-China comments in replies to the question-and-answer site Quora, while publishing cartoons on Pinterest and Pixiv. At other times, the operation has re-circulated propaganda articles across various social networks to try and amplify their reach. “Taken together, we estimate Spamouflage to be the largest known cross-platform covert influence operation to date,” Meta says.

In response, Meta shut down 7,704 accounts, 954 pages, and 15 groups on Facebook tied to the covert op. The company also uncovered “links to individuals associated with Chinese law enforcement,” but it refrained from publicizing the evidence to prevent the Chinese propaganda operation from learning how the company tracks its activities, Meta tells PCMag

“Whenever we attributed influence operations, we do it based on a combination of technical and behavioral indicators including technical/infrastructure signals, distinctive language errors, posting patterns, etc,” the company adds.

In the meantime, Meta says it tracked the group to “geographically dispersed operators across China who appeared to be centrally provisioned with internet access and content.”

“Each cluster worked to a clear shift pattern, with bursts of activity in the mid-morning and early afternoon, Beijing time, with breaks for lunch and supper, and then a final burst of activity in the evening,” the company says.

But even though the propaganda operation tried to pump out vast amounts of disinformation, the reach was limited, Meta says. Few real-world influencers ever re-shared the group’s content. That's likely because the operation’s content suffered from poor quality control. Meta cites numerous spelling and grammar mistakes, an indicator the group was auto-translating content from Chinese without any proofreading. The operation would also post pro-China replies to content on Quora, even though it had nothing to do with the topic.

About 560,000 users followed the group’s pages on Facebook. But Meta notes the pages “appear to have been purchased from third parties in other countries, notably Vietnam and Bangladesh.” These same pages also promoted products like phone cases, lingerie, clothing, and children’s accessories, prior to them being acquired.

“The operators often appear to have begun using these accounts and Pages without making any alterations—leading to highly idiosyncratic behaviors where, for example, a Page that had been posting lingerie ads in Chinese abruptly switched to English and posted organic content about riots in Kazakhstan,” Meta adds.