WASHINGTON — It was a lucrative business. For several years, Richard Pinedo, a Southern California computer science major, would open bank accounts in his name and sell them online to shadowy purchasers for cash. In other cases, he served as a middle man, buying accounts in other people’s names and flipping them on the internet. The operation was illegal, “designed to circumvent the security features of large online digital payment companies,” according to court papers. The company Mr. Pinedo...