Facebook disabled 66 profiles and pages run by a company claiming to sell user data scraped off the social network's platform. Facebook also sent a a cease and desist letter to the company, called Social Data Hub, whose CEO was quoted in Russian telling Inc. that his company is similar to Cambridge Analytica.

Facebook is still investigating the kinds of data Social Data Hub had access to, Facebook spokesman Matt Steinfeld said on Thursday. It could range from information publicly posted on Facebook users' profiles to privately posted content, depending on the methods Social Data Hub used to scrape the data.

"Scraping of all kinds continues to be a challenge across the internet," Facebook said in a statement. "Since it's difficult to prevent and often hard to detect once it's happened, we will be working more closely with other companies and independent experts to share information so we can more quickly disrupt this activity."

Facebook's efforts to stop Social Data Hub reflect a larger problem on social media. Major platforms like Facebook and Twitter invite allow users to make as much of their data public as they want, but this makes it possible for other entities to aggregate large caches of data for their own use.

"Even though it's public, people expect us to do all we can so that unauthorized folks aren't getting access to their information," Steinfeld said.

It's one more way that users may feel uncomfortable with how using companies like Facebook affects their privacy. That worry is very acute right now as Facebook recovers from a major data privacy scandal in which political consultancy Cambridge Analytica improperly obtained data on 83 million Facebook users in March, as well as a data breach affecting 50 million users in September.

On its website, Social Data Hub says it has a copy of the "Russian part of Facebook," as well as data from other US-based social media sites including Twitter and Tumbler, and Russian social media sites Odnoklassniki and VKontakte.

In an emailed statement, Social Data Hub CEO Artur Khachuyan said the company doesn't scrape data outside of Russia. "No one just downloaded Facebook profiles, especially the data of citizens of other countries, except Russia," Khachuyan said. "In Russia, such work is permitted by federal law No. 152 (this is analogous to the GDPR)."

Khachuyan also said Fubutech, an affiliated business that works with governments, is developing scraping technology for government clients but doesn't scrape the data itself. Finally, he said that he teaches journalism courses that include using scraped data. Though the classes are focused on using public data from governments, some students scraped social media data, a Social Data Hub representative said.

Some of the deleted Facebook accounts were from students who did carry out data scraping, Khachuyan said, "but all the data was deleted by them, and the logs were provided on Facebook. We are waiting for the speedy unlocking of our accounts. Unfortunately, we failed to quickly contact the Russian branch of Facebook."

Steinfeld said that companies that scrape publicly posted data from Facebook are the hardest for the company to detect, because they don't have to register an account with Facebook to carry out their activities. Facebook does have techniques for detecting such companies. Steinfeld declined to discuss the techniques on the record, so that the companies wouldn't learn about them in the press.

In the cease and desist letter, dated Oct. 8, Facebook wrote that, "The Social Data Hub website acknowledges that the company uses web scraping to gather data from Facebook and Instagram."

The contents of the cease and desist letter were read to CNET.

In the letter to Social Data Hub, Facebook also wrote, "In an April 2018 press interview you stated that your company collects data without the permission of the end users. You have further publicly stated that Social Data Hub and Fubutech clients include governmental entities, corporations and media outlets. And Facebook has reason to believe your work for the government has included photos from individual's personal social media accounts in order to identify them."

Facebook said in its statement that it expects to find and remove more content from Social Data Hub on its service.

This is a developing story.