Dr. Adam Aviv, Associate Professor of Computer Science at GW who conducts research on mobile authentication and how users select PINs/passcodes on their phone, was quoted by The Wall Street Journal in the article, "A Basic iPhone Feature Helps Criminals Steal Your Entire Digital Life." The article details the danger of someone learning your phone’s passcode as this feature is becoming a way for criminals to gain access to steal one’s entire digital life.
Here is an excerpt from the article: “It was only a matter of time before an attacker would use shoulder surfing or social engineering,” said Aviv. Relying on a phone as a trusted device fails in such cases, he added."
Read the full article in The Wall Street Journal.