The parent company of Facebook and Instagram said on Wednesday it has taken down more than 600 accounts, pages and groups connected to a Chinese influence operation spreading COVID-19 disinformation, including an account purporting to be a fictitious Swiss biologist.

The China-based network was one of six Meta, formerly know as Facebook, removed in November for abusing its platforms, a reminder that bad actors around the world are using social media to promote false information and harass opponents.

The other operations included one supporting Hamas and two others, based in Poland and Belarus, that were focused on the migration crisis on the countries' shared border.

Meta also removed a network tied to a European anti-vaccination conspiracy movement that harassed doctors, elected officials and journalists on Facebook and other internet platforms, as well as a group of accounts in Vietnam that reported activists and government critics to Facebook in attempts to get them banned from the social network.

The China-based operation came to light after the company was alerted to an account purporting to be a Swiss biologist named Wilson Edwards (no such person exists). The account posted claims on Facebook and Twitter in July that the U.S. was pressuring World Health Organization scientists to blame China for the COVID-19 virus. The posts alleging U.S. intimidation soon appeared in Chinese state media stories.

"This campaign was a hall of mirrors, endlessly reflecting a single fake persona," Ben Nimmo, who investigates influence operations at Meta, wrote in the company's report. Meta connected the operation to individuals in China and people "associated with Chinese state infrastructure companies located around the world," he said.

The Chinese operation was an example of what Meta calls "coordinated inauthentic behavior," in which adversaries use fake accounts for influence operations, as Russian operatives did by impersonating Americans on Facebook in the run-up to the 2016 U.S. presidential election.

But recently, Meta's security team has expanded its focus to root out accounts of real people who are working together to cause harm both on Facebook and offline.

That was the rationale used to remove a network of accounts in Italy and France connected to an anti-vaccination movement known as V_V. According to a report from the research firm Graphika, the group largely coordinates on the messaging app Telegram, but "appears to primarily target Facebook, where its members display the group's double V symbol in their profile pictures and swarm the comments sections of posts advocating for COVID-19 vaccines with hundreds of abusive messages." Graphika said the group has also defaced health facilities and attempted to disrupt public vaccination programs.

Meta said the people behind the network used real, duplicate and fake accounts to comment on Facebook posts in droves and intimidate people. That breaks the company's rules against "brigading." Meta said it is not banning all V_V content but will take further action if it finds more rule-breaking behavior. It did not say how many accounts it removed in the network.

The company acknowledged that even as it becomes quicker at detecting and removing accounts that break its rules, it is playing a cat-and-mouse game.

"Adversarial networks don't strive to neatly fit our policies or only violate one at a time," Nathaniel Gleicher, Meta's head of security policy, wrote in a blog post on Wednesday. "We build our defenses with the expectation that they will not stop, but rather adapt and try new tactics. "

Editor's note: Meta pays NPR to license NPR content.