Much of the empire built by Alex Jones, the Infowars founder and social media shock jock, vanished this summer when Facebook suspended Mr. Jones for 30 days and took down four of his pages for repeatedly violating its rules against bullying and hate speech. YouTube, Apple and other companies also took action against Mr. Jones. But a private Infowars Facebook group with more than 110,000 members, which had survived the crackdown, remained a hive of activity.
In Mr. Jones's absence, the group continued to fill with news stories, Infowars videos and rants about social media censorship. Users also posted the sort of content — hateful attacks against Muslims, transgender people and other vulnerable groups — that got Mr. Jones suspended. And last week, when Mr. Jones's suspension expired, he returned to the group triumphantly.
"My 30-day Facebook ban is up!" Mr. Jones announced.
Mr. Jones built his Facebook audience on pages — the big public megaphones he used to blast links, memes and videos to millions of his followers. In recent months, though, he and other large-scale purveyors of inflammatory speech have found refuge in private groups, where they can speak more openly with less fear of being punished for incendiary posts.
Several private Facebook groups devoted to QAnon, a sprawling pro-Trump conspiracy theory, have thousands of members. Regional chapters of the Proud Boys, a right-wing nationalist group that Twitter suspended last month for its "violent extremist" nature, maintain private Facebook groups, which they use to vet new members. And anti-vaccination groups have thrived on Facebook, in part because they are sometimes recommended to users by the site's search results and "suggested groups" feature.
Facebook's fight against disinformation and hate speech will be a topic of discussion on Capitol Hill on Wednesday, when Sheryl Sandberg, the company's chief operating officer, will join Jack Dorsey, Twitter's chief executive, to testify in front of the Senate Intelligence Committee.
When it comes to public-facing pages, Ms. Sandberg will have plenty of company actions to cite. Facebook has taken many steps to clean up its platform, including hiring thousands of additional moderators, developing new artificial-intelligence tools and breaking up coordinated influence operations ahead of the midterm elections.
But when it comes to more private forms of communication through the company's services — like Facebook groups, or the messaging apps WhatsApp and Facebook Messenger — the social network's progress is less clear. Some experts worry that Facebook's public cleanup may be pushing more toxic content into these private channels, where it is harder to monitor and moderate.
Misinformation is not against Facebook's policies unless it leads to violence. But many of the private groups reviewed by The New York Times contained content and behavior that appeared to violate other Facebook rules, such as rules against targeted harassment and hate speech. In one large QAnon group, members planned a coordinated harassment campaign, known as Operation Mayflower, against public figures such as the actor Michael Ian Black, the late-night host Stephen Colbert and the CNN journalist Jim Acosta. In the Infowars group, posts about Muslims and immigrants have drawn threatening comments, including calls to deport, castrate and kill people.