In November 2016, shortly after Trump’s victory in the Presidential election, a Twitter account called ‘Sleeping Giants’ (@slpng_giants) was created. Exactly a week after the election, it sent out its first tweet, alerting a company called Social Finance that they were advertising with the right-wing news site Breitbart. About half an hour later, Social Finance tweeted back, agreeing to halt the advertising.

Fast-forward a month, and the Sleeping Giants account makes a request to its followers: go to the Breitbart site, screenshot one of the advertisements you see, and tweet the screenshot to the company that is advertising. It sounds like an idea that would never work: a group of anonymous cyber-vigilantes, crowdsourcing a means of cutting off the funding to one of the most prominent and powerful news organisations on the internet. But, somehow, it does work. The tweets flood in to the offending companies, and the Sleeping Giant account retweets them to their 120,000 followers. How many companies pull their advertising? Well, according to Sleeping Giants, the exact number is 2,822. Nearly three thousand companies have dropped Breitbart.

But why do these companies advertise with Breitbart to begin with, and why are they willing to drop the advertisements if they’ve already agreed to host them on Breitbart’s site? Well, the answer is that most of the companies don’t actually know that they’re advertising with Breitbart. The way that advertising online generally works is that companies use services like Google AdSense that have access to advertising space on millions of domains. The adverts are then placed on domains that fit in the target demographic of the advertising company. The only way for companies to avoid specific domains is by using their blacklist, which prevents advertisements going up on sites they don’t want to be associated with. Sleeping Giant alerts companies to the fact that they are advertising on Breitbart, and convinces them to add the companies to their blacklist, so that the ad-distributors stop putting their ads on Breitbart’s site.

This takes us to Sleeping Giants’ real ambition: convince the third parties that supply the advertisements to pull ads from Breitbart entirely. So far, they haven’t had much luck. Sleeping Giants have specifically targeted Google AdSense and the Facebook Audience Network, two of the biggest ad-distributors on the web. They haven’t yet received a response. In June this year, Sleeping Giants raised over $8,000 from online donors, which they used to put up a billboard near Amazon headquarters, asking them to remove their ads from Breitbart. Again, no response.

Another problem for Sleeping Giants is the fact that the bulk of Breitbart’s funding doesn’t come from advertisements on the site, but from Bob Mercer, the man who established the ‘Make America Number 1’ Super PAC, which funded both Ted Cruz and Donald Trump, and proclaimed itself to be the ‘Defeat Crooked Hillary’ Super PAC. Mercer has donated roughly $35 million to political campaigns, and invested $11 million in Breitbart in 2011. Sleeping Giants might be effective in getting companies to pull their advertisements from Breitbart’s site, but Mercer is unlikely to let the news site collapse entirely.

Even with these obstacles, Sleeping Giants has been a stunning success and the growth of its Twitter and Facebook following has been exponential. Breitbart isn’t relaxed about the impact of the campaign, as shown by their call for a boycott of Kellogg’s after Sleeping Giants managed to get the multinational company to pull its advertising on the site. So, this anonymous group might not yet be able to slay Breitbart, but they’ve dealt them a substantial blow.