Maksymilian Rafailovych "Max" Levchin; born July 11, 1975) is a Ukrainian-American software engineer and businessman. In 1998, he co-founded the company that eventually became PayPal. Levchin made contributions to PayPal's anti-fraud efforts and was the co-creator of the Gausebeck-Levchin test, one of the first commercial implementations of a CAPTCHA challenge response human test. He founded or co-founded the companies Slide.com, HVF, and Affirm. He was an early investor in Yelp and was their largest shareholder in 2012. He left a leadership role in Yelp in 2015. Levchin was a producer for the movie Thank You for Smoking. Born in Kyiv, Ukrainian SSR to a Ukrainian-Jewish family, Levchin moved to the United States and settled in Chicago in 1991. In an interview with Emily Chang of Bloomberg, Levchin discussed his overcoming adversity as a child. He had respiratory problems and doctors doubted his chance of living. With guidance from his grandmother and his parents he took up the clarinet to expand his lung capacity. He attended Mather High School, and then the University of Illinois at Urbana-Champaign, where he earned a bachelor's degree in computer science in 1997. In 1998, Levchin and Peter Thiel founded Fieldlink, a security company that allowed users to store encrypted data on their PalmPilots and other PDA devices for handheld devices to serve as "digital wallets". After changing the company name to Confinity, they developed a popular payment product known as PayPal and focused on digital transfers of funds by PDA. The company merged with X.com in 2000, and in 2001, the company adopted the name PayPal after its main product. PayPal, Inc. went public in February 2002, and in July 2002 was acquired by eBay. Levchin's 2.3% stake in PayPal was worth approximately $34 million at the time of the acquisition. Levchin is primarily known for his contributions to PayPal's anti-fraud efforts and is also the co-creator of the Gausebeck-Levchin test, one of the first commercial implementations of a CAPTCHA. In 2002, he was named to the MIT Technology Review TR100 as one of the top 100 innovators in the world under the age of 35, as well as Innovator of the Year. Levchin is one of a group of roughly twenty founders and former employees of PayPal who have become referred to as the "PayPal Mafia", due to their success in founding and investing in tech companies after leaving PayPal.