Have you visited Showtime's website recently? If so, you may be a cryptocurrency miner. An observant Twitter user was the first to sound an alarm last month that the source code for the Showtime Anytime website contained a tool that was secretly hijacking visitors' computers to mine Monero, a Bitcoin–like digital currency focused on anonymity. It's still not clear how the tool got there, and Showtime quickly removed it after it was pointed out. But if it was the work of hackers, the episode is actually part of a larger trend: security experts have seen a spike in cyberattacks this year that are aimed at stealing computer power for mining operations.