Byline: DOUG BOCK CLARK PHOTOGRAPH JO�O CANZIANI

EVERYTHING YOU SAY CAN AND WILL BE USED AGAINST YOU

PROFILES A COMPUTER SCIENTIST WHO MINES DATA TO EXPOSE FAR-RIGHT EXTREMISTS.

The email arrived just as Megan Squire was starting to cook Thanksgiving dinner. She was flitting between the kitchen, where some chicken soup was simmering, and her living room office, when she saw the subject line flash on her laptop screen: "LOSer Leak." Squire recognized the acronym of the League of the South, a neo-Confederate organization whose leaders have called for a "second secession" and the return of slavery. An anonymous insider had released the names, addresses, emails, passwords, and dues-paying records of more than 4,800 members of the group to a left-wing activist, who in turn forwarded the information to Squire, an expert in data mining and an enemy of far-right extremism.

Fingers tapping across the keyboard, Squire first tried to figure out exactly what she had. She pulled up the Excel file's metadata, which suggested that it had passed through several hands before reaching hers. She would have to establish its provenance. The data itself was a few years old and haphazardly assembled, so Squire had to rake the tens of thousands of information-filled cells into standardized sets. Next, she searched for League members near her home of Gibsonville, North Carolina. When she found five, she felt a shiver. She had recently received death threats for her activism, so she Googled the names to find images, in case those people showed up at her door. Then she began combing through the thousands of other names. Two appeared to be former South Carolina state legislators, one a firearms industry executive, another a former director at Bank of America.

Once she had a long list of people to investigate, Squire opened a database of her own design-named Whack-a-Mole-which contains, as far as anyone can tell, the most robust trove of information on far-right extremists. When she cross-checked the names, she found that many matched, strengthening her belief in the authenticity of the leak. By midafternoon, Squire was exchanging messages via Slack with an analyst at the Southern Poverty Law Center, a 46-year-old organization that monitors hate groups. Squire often feeds data to the SPLC, whose analysts might use it to provide information to police or to reveal white supremacists to their employers, seeking to get them fired. She also sent several high-profile names from the list to another contact, a left-wing activist who she knew might take more radical action-like posting their identities and photos online, for the public to do with what it would.

Squire, a 45-year-old professor of computer science at Elon University, lives in a large white house at the end of a suburban street. Inside are, usually, some combination of husband, daughter, two step-children, rescue dog, and cat. In her downtime she runs marathons and tracks far-right extremists. Whack-a-Mole, her creation, is a set of programs that monitors some 400,000 accounts of white nationalists on Facebook and other...