One morning two weeks ago, security researcher Jeroen van der Ham was traveling by train in the Netherlands when his iPhone suddenly displayed a series of pop-up windows that made it nearly impossible to use his device.
“My phone was getting these popups every few minutes and then my phone would reboot,” he wrote to Ars in an online interview. “I tried putting it in lock down mode, but it didn't help.”
To van der Ham’s surprise and chagrin, the same debilitating stream of pop-ups hit again on the afternoon commute home, not just against his iPhone but the iPhones of other passengers in the same train car. He then noticed that one of the same passengers nearby had also been present that morning. Van der Ham put two and two together and fingered the passenger as the culprit.