(CNN) Sen. Mark Warner, the top Democrat on the Senate intelligence committee, said Facebook officials told Senate staff Wednesday that the ads purchased by Russians urged users to "Like" certain political groups -- which then led to political messages flooding their Facebook news feeds.

"This is kind of a whole ecosystem, where you have ads are one component, but then you have accounts and if those accounts, like a certain group ... 'Mark Warner for Senate,' whatever, pops up much higher in your newsfeed. And you as a person don't screen that," Warner said Thursday.

Facebook's chief security officer said in a statement Wednesday that Russian "trolls" purchased $100,000 in ads over the last two years -- including a handful of ads which specifically mentioned Hillary Clinton and Donald Trump.

A congressional source familiar with the Facebook briefings Wednesday said that the idea of the ads was not to directly influence Facebook users to vote for one candidate or another based on that ad, but instead to plug them into groups which would then inundate their feeds with political messages to try and influence their actions.

Read More