Like the millions of Americans who watched in horror as a long, contentious, and bigotry-filled campaign season ended with Donald Trump winning his bid for the Oval Office, the group of friends behind Sleeping Giants were feeling, as one of them puts it, pretty “bummed out” in the weeks following Election Day 2016. But after it became clear that former Breitbart executive Steve Bannon would be appointed to a senior position in the Trump administration, they decided to respond by doing what everyone does when they spot something bad in the world: Start tweeting about it.

Relying on a combination of digital media savvy, Google research, and their intuition about major corporations’ fondness for being associated with stuff like this, the friends correctly guessed that “programmatic advertising” was responsible for many of the ads that appear on Breitbart. Rather than manually place digital ads, companies large and small will pay brokers—Google, Amazon, and the like—to place them all over the Internet, irrespective of the destination site’s content. Programmatic advertising is why, for example, a reader who scrolls to the bottom of a Breitbart article might come upon the smiling face of Bernie Sanders, urging them to sign on as a Medicare for All co-sponsor.

Brokers, however, also allow clients to place potential ad locations on a blacklist. All they have to do is ask. Armed with this information, Sleeping Giants began tweeting at companies’ official handles, notifying them of their perhaps-unwitting presence on Breitbart and offering to help fix it. When a community of like-minded users began following suit, Sleeping Giants authored a step-by-step guide to the process, pointedly reminding newbies to phrase their overtures in a “non-offensive” way. Many third-party tweets based on this template end with a cheerful, we’re-all-in-this-together refrain that has, as far as I can tell, developed organically: “@slpng_giants can help!”

Since then, the campaign has welcomed new volunteers into the fold and spawned more than a dozen loosely-affiliated international chapters. And while a few of its members know one another in real life, most have never any of the others in person. A spokesman jokingly likens it to a more genteel version of Reservoir Dogs. “Everyone is really friendly, and we all talk and share information,” he says, “but no one knows each other’s real names.” Not that it’s mattered. Less than a year and a half after Sleeping Giants sent its first screenshot to a Breitbart advertiser, their model of polite, carefully-targeted, crowdsourced activism has resulted in nearly 4,000 companies adding the site to their programmatic advertising blacklists.

To date, the people behind Sleeping Giants have elected to remain anonymous, noting that a few of them work in marketing-related fields in which their off-hours activism might be perceived as creating some kind of conflict of interest. The identities of the people who operate a Twitter handle, at least to them, are far less important than what the community has accomplished together. “We’re kind of just administrators at this point,” he says. “It’s cooler that way.” Though he doesn't say as much, it is also easy to imagine how unmasking the campaign's founders might cause opponents to attack the individuals behind it. Collective anonymity can be a handy defense.