Seven months after the Columbian Chemicals hoax, I was in a dim restaurant in St. Petersburg, peering out the window at an office building at 55 Savushkina Street, the last known home of the Internet Research Agency. It sits in St. Petersburg’s northwestern Primorsky District, a quiet neighborhood of ugly Soviet apartment buildings and equally ugly new office complexes. Among the latter is 55 Savushkina; from the front, its perfect gray symmetry, framed by the rectangular pillars that flank its entrance, suggests the grim impenetrability of a medieval fortress. Behind the glass doors, a pair of metal turnstiles stand guard at the top of a short flight of stairs in the lobby. At 9 o’clock on this Friday night in April, except for the stairwell and the lobby, the building was entirely dark.

This puzzled my dining companion, a former agency employee named Ludmila Savchuk. She shook her head as she lifted the heavy floral curtain to take another look. It was a traditional Russian restaurant, with a dining room done up like a parlor from the early 1900s, complete with bentwood chairs and a vintage globe that showed Alaska as part of Russia. Savchuk’s 5-year-old son sat next to her, slurping down a bowl of ukha, a traditional fish soup. For two and a half months, Savchuk told me, she had worked 12-hour shifts in the building, always beginning at 9 a.m. and finishing at 9 p.m., at which point she and her co-workers would eagerly stream out the door at once. “At 9 p.m. sharp, there should be a crowd of people walking outside the building,” she said. “Nine p.m. sharp.” One Russian newspaper put the number of employees at 400, with a budget of at least 20 million rubles (roughly $400,000) a month. During her time in the organization, there were many departments, creating content for every popular social network: LiveJournal, which remains popular in Russia; VKontakte, Russia’s homegrown version of Facebook; Facebook; Twitter; Instagram; and the comment sections of Russian news outlets. One employee estimated the operation filled 40 rooms.

Every day at the Internet Research Agency was essentially the same, Savchuk told me. The first thing employees did upon arriving at their desks was to switch on an Internet proxy service, which hid their I.P. addresses from the places they posted; those digital addresses can sometimes be used to reveal the real identity of the poster. Savchuk would be given a list of the opinions she was responsible for promulgating that day. Workers received a constant stream of “technical tasks” — point-by-point exegeses of the themes they were to address, all pegged to the latest news. Ukraine was always a major topic, because of the civil war there between Russian-backed separatists and the Ukrainian Army; Savchuk and her co-workers would post comments that disparaged the Ukrainian president, Petro Poroshenko, and highlighted Ukrainian Army atrocities. Russian domestic affairs were also a major topic. Last year, after a financial crisis hit Russia and the ruble collapsed, the professional trolls left optimistic posts about the pace of recovery. Savchuk also says that in March, after the opposition leader Boris Nemtsov was murdered, she and her entire team were moved to the department that left comments on the websites of Russian news outlets and ordered to suggest that the opposition itself had set up the murder.

Savchuk told me she shared an office with about a half-dozen teammates. It was smaller than most, because she worked in the elite Special Projects department. While other workers churned out blandly pro-Kremlin comments, her department created appealing online characters who were supposed to stand out from the horde. Savchuk posed as three of these creations, running a blog for each one on LiveJournal. One alter ego was a fortuneteller named Cantadora. The spirit world offered Cantadora insight into relationships, weight loss, feng shui — and, occasionally, geopolitics. Energies she discerned in the universe invariably showed that its arc bent toward Russia. She foretold glory for Vladimir Putin, defeat for Barack Obama and Petro Poroshenko. The point was to weave propaganda seamlessly into what appeared to be the nonpolitical musings of an everyday person.

In fact, she was a troll. The word “troll” was popularized in the early 1990s to denounce the people who derailed conversation on Usenet discussion lists with interminable flame wars, or spammed chat rooms with streams of disgusting photos, choking users with a cloud of filth. As the Internet has grown, the problem posed by trolls has grown more salient even as their tactics have remained remarkably constant. Today an ISIS supporter might adopt a pseudonym to harass a critical journalist on Twitter, or a right-wing agitator in the United States might smear demonstrations against police brutality by posing as a thieving, violent protester. Any major conflict is accompanied by a raging online battle between trolls on both sides.

As Savchuk and other former employees describe it, the Internet Research Agency had industrialized the art of trolling. Management was obsessed with statistics — page views, number of posts, a blog’s place on LiveJournal’s traffic charts — and team leaders compelled hard work through a system of bonuses and fines. “It was a very strong corporate feeling,” Savchuk says. Her schedule gave her two 12-hour days in a row, followed by two days off. Over those two shifts she had to meet a quota of five political posts, 10 nonpolitical posts and 150 to 200 comments on other workers’ posts. The grueling schedule wore her down. She began to feel queasy, she said, posting vitriol about opposition leaders of whom she had no actual opinion, or writing nasty words about Ukrainians when some of her closest acquaintances, including her own ex-husband, were Ukrainian.

Employees were mostly in their 20s but were drawn from a broad cross-section of Russian society. It seemed as if the agency’s task was so large that it would hire almost anyone who responded to the many ads it posted on job boards, no matter how undereducated or politically ignorant they were. Posts teemed with logical and grammatical errors. “They were so stupid,” says Marat Burkhardt, who worked for two months in the department of forums, posting 135 comments a day on little-read message boards about remote Russian towns. “You see these people with a lot of tattoos. They’re so cool, like they’re from New York; very hip clothing, very hip tattoos, like they’re from Williamsburg. But they are stupid.” In office conversation, they used gay slurs to refer to Petro Poroshenko and called Barack Obama a monkey. Management tried to rectify their ignorance with grammar classes. Others had “politology” classes to outline the proper Russian point of view on current events.