A Russian propaganda group purchased ads on Facebook during the 2016 election. Here’s what that means.

Facebook announced Wednesday that a Russian propaganda organization used the social media platform to purchase $100,000 of political advertising.

Here’s what you need to know about this news:

What was found?

Facebook found 470 inauthentic accounts associated with approximately 3,000 political ads from June 2015 to May 2017. The ad purchases and accounts are affiliated with a Russian “troll farm,” dubbed the Internet Research Agency, which spreads pro-Russian propaganda and false information across the World Wide Web.

Most of the ads did not contain references to the 2016 U.S. presidential election, voting or the candidates. “Rather, the ads and accounts appeared to focus on amplifying divisive social and political messages across the ideological spectrum — touching on topics from LGBT matters to race issues to immigration to gun rights,” Facebook’s Chief Security Officer Alex Stamos said in a blog post on the company’s website.

Facebook also conducted a wider search for political ads that potentially originated from Russia. The company found $50,000 worth of spending on 2,200 ads. A Facebook spokesperson, however, cautioned that this group of ads carried a low amount of certainty because the company’s search included sources with weak connections to Russia.

How does the Russian propaganda machine work? Special correspondent Nick Schifrin talked to someone who used to work as a “troll” inside the Internet Research Agency. Watch his July 2017 report from “Inside Putin’s Russia.”

What is the Internet Research Agency?

“The agency had become known for employing hundreds of Russians to post pro-Kremlin propaganda online under fake identities, including on Twitter, in order to create the illusion of a massive army of supporters,” journalist Adrian Chen wrote in 2015 in the New York Times Magazine.

Chen reported that the agency was responsible for false reports of toxic fumes in Louisiana and an outbreak of Ebola in Atlanta, both in 2014.

Learn more about the Internet Research Agency from this 2015 conversation between PBS NewsHour’s Jeffrey Brown and journalist Adrian Chen.

Why it’s important

In January, the U.S. intelligence community concluded that Russian President Vladimir Putin led a campaign to influence the 2016 U.S. presidential election. Paid trolls — social media users who were compensated to deliberately post controversial content — and the social media accounts of the pro-Kremlin television network RT were part of this effort, according to their report.

What Facebook found is “one small piece of this larger, consistent, Russian effort,” John Sipher, a former CIA agent who ran the agency’s Russia program for three years, told the NewsHour.

“This is a big deal because I think it’s more evidence of a coordinated Russian attack against our system,” Sipher said.

And for those who suggest that $100,000 in ads is not much: “This is just one troll farm that Facebook has proven” was Russian, Sipher said. “I’m sure there’s all kinds of other stuff that hasn’t been picked up on yet.”

In addition to the ad buying, an investigation published late Thursday by The New York Times, with research from the cybersecurity company FireEye, detailed other ways that suspected Russian trolls disseminated false and hacked information.

Rep. Adam Schiff, the ranking Democrat on the House Intelligence Committee, told the Washington Post that Facebook’s disclosure is a “profound warning to us and others about future elections.” A question left to answer, he said, is whether any of the pro-Russian trolls coordinated with President Trump’s 2016 campaign team.

What’s next?

Stamos, the chief security officer, said Facebook has since shut down the 470 suspicious accounts and pages.

“We have shared our findings with U.S. authorities investigating these issues, and we will continue to work with them as necessary,” Stamos said.

But Facebook has not shared copies of the ads with the public, and does not plan to, a Facebook spokesperson told the NewsHour. A Facebook official told the Washington Post that “our data policy and federal law limit our ability to share user data and content, so we won’t be releasing any ads.”

Facebook’s refusal to share the ads has drawn criticism from eBay founder, philanthropist and First Look Media founder Pierre Omidyar and former Federal Election Commission Chairman Trevor Potter.

Stamos noted that Facebook has made improvements to weed out fake accounts based on their activity on the platform and end the spread of fake news in the past year, with more improvements planned.

“We are looking at how we can apply the techniques we developed for detecting fake accounts to better detect inauthentic pages and the ads they may run,” Stamos said. “We are also experimenting with changes to help us more efficiently detect and stop inauthentic accounts at the time they are being created.”