How Christmas became one of the biggest days of the year for hackers

Five years ago this Christmas, some people who woke up to a new Xbox or PlayStation hoping to play the latest video games might as well have received a lump of coal. It turned out to be a harbinger of holiday computer grief to come.

A hacking group called the Lizard Squad picked Dec. 24, 2014, to launch an attack against the computer networks of the two gaming systems, and they succeeded in knocking the networks offline for much of the next two days — temporarily turning $350 gaming consoles...