Marty Weiner has spent more than a decade on the hidden side of the internet, running the teams that keep spam, bots and bad actors from overrunning a platform.

He joined Pinterest as its second engineer and spent four and a half years helping it scale, eventually managing BlackOps, the team that fought spam. Within six months that team halved the number of people clicking on spam, and within a year it went from needing hours to stop an attack to dismantling attacks in milliseconds.

In 2015 Reddit hired him as its first CTO. He doubled the engineering team within six months and built an anti-evil team that cut incoming spam reports by about 60 percent, on a site with roughly 234 million monthly visitors.

That work taught him a simple rule: to stop fraud, make it more costly to commit than the economic incentive. He now applies it as co-founder and CTO of VerifyYou, the company behind HumanCheck, which confirms that a real, unique, live person is on the other end of an account.

Marty co-hosts the podcast Last Humans in the Loop and speaks often about scaling, trust and AI, with talks at QCon, SXSW, Startupfest, Civo Navigate and Tom Tom Festival.