In the fall of 2016, Keegan Hankes, an analyst at the Southern Poverty Law Center, paid a visit to the neo-Nazi website the Daily Stormer. This was not unusual; part of Hankes’ job at the civil rights organization was to track white supremacists online, which meant reading their sites. But as Hankes loaded the page on his computer at SPLC’s headquarters in Montgomery, Alabama, something caught his eye: a pop-up window that announced “Checking your browser before accessing … Please allow up to 5 seconds.” In fine print, there was the cryptic phrase “DDoS protection by Cloudflare.” Hankes, who had worked at SPLC for three years, had no idea what Cloudflare was. But soon he noticed the pop-up appearing on other hate sites and started to poke around.

There’s a good chance that, like Hankes, you haven’t heard of Cloudflare, but it’s likely you’ve viewed something online that has passed through its system. Cloudflare is part of the backend of the internet. Nearly 10 percent of all requests for web pages go through its servers, which are housed in 118 cities around the world. These servers speed along the delivery of content, making it possible for clients’ web pages to load more quickly than they otherwise would. But Cloudflare’s main role is protection: Its technology acts as an invisible shield against distributed denial of service (DDoS) attacks—hacker campaigns that disable a website by overwhelming it with fake traffic. The company has more than 7 million customers, from individual bloggers who pay nothing for basic security services to Fortune 50 companies that pay up to a million dollars a year for guaranteed 24-hour support.

Hankes wanted to learn something about Cloudflare’s business, and what really interested him was finding out who Cloudflare was protecting. After a few months of research, he felt confident he’d uncovered something important, and on March 7, 2017, he penned a blog post that denounced Cloudflare for “optimizing the content of at least 48 hate websites.” Those sites included Stormfront, the grandfather of white-nationalist online message boards, and the Daily Stormer, at that time one of the most important hate sites on the internet. A virulently anti-­Semitic publication, the Daily Stormer was founded in 2013 by a thuggishly enigmatic white supremacist named Andrew Anglin. (“Total Fascism” was the upbeat name of one of his earlier publications.)

February 2018. Subscribe to WIRED. Sean Freeman

Without Cloudflare’s protection, the Daily Stormer and those other sites might well have been taken down by vigilante hackers intent on eliminating Nazi and white-­supremacist propaganda online. Hankes and the SPLC weren’t accusing Cloudflare of spouting racist ideology itself, of course. It was more that Cloudflare was acting like the muscle guarding the podium at a Nazi rally.

Matthew Prince, the 43-year-old CEO of Cloudflare, didn’t bother responding to the SPLC’s pointed accusation. In fact, he has only the haziest recollection of hearing about it. He might have seen a mention on Twitter. He’s not sure. Prince is a genial, Ivy League–educated Bay Area resident who once sat in on lectures by a law professor named Barack Obama—the type of person you would expect to have a vivid impression of being denounced by a prominent civil rights organization. But for Prince the criticism was nothing new. At Cloudflare, he was in the business of protecting all kinds of clients, including some whose views vaulted way outside the boundaries of acceptable discourse. He’d already been accused of helping copyright violators, sex workers, ISIS, and a litany of other deplorables. It was hardly a surprise to him that neo-Nazis would be added to the list. Come late summer, however, he would no longer be able to take that breezy attitude. Prince didn’t realize it at the time, but that SPLC blog post was the first indication of the trouble to come. Five months later, Prince would be forced to make a very public decision about the Daily Stormer, one made against his own best judgment and that presented some of the thorniest and most perplexing challenges to free speech since the ACLU defended neo-Nazis who planned to march in Skokie, Illinois, 40 years ago.