For Graham Ivan Clark, the online mischief-making started early. By the age of 10, he was playing the video game Minecraft, in part to escape what he told friends was an unhappy home life. In ...

At 15, he joined an online hackers’ forum. By 16, he had gravitated to the world of Bitcoin, appearing to involve himself in a theft of $856,000 of the cryptocurrency, though he was never charged for ...