The campuses of the tech industry are famous for their lavish cafeterias, cushy shuttles, and on-site laundry services. But on a muggy February afternoon, some of these companies’ most important work is being done 7,000 miles away, on the second floor of a former elementary school at the end of a row of auto mechanics’ stalls in Bacoor, a gritty Filipino town 13 miles southwest of Manila.

When I climb the building’s narrow stairwell, I need to press against the wall to slide by workers heading down for a smoke break. Up one flight, a drowsy security guard staffs what passes for a front desk: a wooden table in a dark hallway overflowing with file folders.

Past the guard, in a large room packed with workers manning PCs on long tables, I meet Michael Baybayan, an enthusiastic 21-year-old with a jaunty pouf of reddish-brown hair. If the space does not resemble a typical startup’s office, the image on Baybayan’s screen does not resemble typical startup work: It appears to show a super-close-up photo of a two-pronged dildo wedged in a vagina. I say appearsbecause I can barely begin to make sense of the image, a baseball-card-sized abstraction of flesh and translucent pink plastic, before he disappears it with a casual flick of his mouse.

Baybayan is part of a massive labor force that handles “content moderation”- the removal of offensive material -for US social-networking sites. As social media connects more people more intimately than ever before, companies have been confronted with the Grandma Problem: Now that grandparents routinely use services like Facebook to connect with their kids and grandkids, they are potentially exposed to the Internet’s panoply of jerks, racists, creeps, criminals, and bullies. They won’t continue to log on if they find their family photos sandwiched between a gruesome Russian highway accident and a hardcore porn video. Social media’s growth into a multibillion-dollar industry, and its lasting mainstream appeal, has depended in large part on companies’ ability to police the borders of their user-generated content—to ensure that Grandma never has to see images like the one Baybayan just nuked.