(CNN) Facebook acknowledged this week that it had unwittingly sold $100,000 worth of political ads on its site to a Russia company which has done pro-Kremlin work in the past. It's not clear how extensive this effort was but the development comes amid the ongoing special counsel probe led by Robert Mueller into Russia interference in the 2016 election and the possibility of collusion between the foreign power and the Trump campaign.

Wondering how something like this could happen with Facebook, I reached out to CNN Tech's Seth Fiegerman for answers. Our conversation, conducted via email and lightly edited for flow, is below. (Make sure to check out Seth's big explainer on Facebook's Russia problem here .)

Cillizza: Let's start basic. How does Facebook sell political ads?

Fiegerman: If you're picturing a "Mad Men" scenario where Facebook executives sit in suits (or hoodies) around a table brokering all their ad deals, it's probably time to retire that image.

Facebook representatives may get directly involved in helping a particularly big operation, like a presidential campaign. But a key part of Facebook's ad business is the self-service model. You or I can create an ad account, pick an article or Facebook page we want to promote, determine how much we want to spend on it and then select various targeting options. And Facebook's targeting potential is impressive: They know your age, location, gender and interests. As I've reported before, Facebook has long touted its ability to influence voting decisions just as it influences buying decisions

Cillizza: How much money was spent on political ads during the 2016 campaign? And what was the breakdown between D and R?

Fiegerman: This hits on a deeper concern. There is very little transparency about how much is spent on political advertising online. It's not a data point the big tech companies break out. The 2016 election was expected to be the first where : This hits on a deeper concern. There is very little transparency about how much is spent on political advertising online. It's not a data point the big tech companies break out. The 2016 election was expected to be the first where overall digital ad spending hit the $1 billion mark , according to third party estimates. That still trails behind the billions spent on TV ads, but it's certainly nothing to sneeze at. Facebook, along with Google, was well positioned to claim a big chunk of that spending.

Cillizza: What is Facebook's ad-screening process? How can a foreign government slip through that screen?

Fiegerman: On its website, Facebook says it typically reviews ads within 24 hours. It may ban ads for a long list of reasons, including promoting illegal products, adult content, profanity or engages in discriminatory practices. But keep in mind: there are millions of companies and individuals buying ads on the social network. That's a lot to vet.

The ads placed by the Russian-linked accounts may not have violated those specific guidelines, but the use of a network of fraudulent accounts certainly breaks Facebook's rules. This is an ongoing challenge for Facebook. It continues to develop technical solutions for detecting fake accounts and pages.

Cillizza: Is there any sense of whether this one $100,000 ad buy was an isolated incident or a small piece of a much-bigger spending/persuasion operation?

Fiegerman: The fake accounts behind the ad buy are said to have been created by the Internet Research Agency, a Russian company that has been described as a "troll farm" and is known for engaging in propaganda campaigns. The goal, as described by Facebook, was to "focus on amplifying divisive social and political messages." That included topics like immigration and gun rights.

Cillizza: Finish this sentence: "The damage done to Facebook from this story is __________." Now, explain.

Fiegerman: "Significant."

The amount spent on ads may be small, but has the potential to further damage public trust in Facebook.

Days after the US election, Facebook CEO Mark Zuckerberg said he thought the idea that fake news stories on Facebook influenced the election was "crazy." But his company has spent much of this year trying to curb the spread of fake news. This latest controversy will only add to concerns about how Facebook manages its tremendous power. And it comes at a time when there is mounting antitrust scrutiny of the big tech companies in the US and Europe.