A ransomware attack hit servers around the world yesterday. The infected computers displayed a message in red type over a black screen that read, "Oops, your important files are encrypted," demanding a $300 bitcoin ransom from users to recover the data. Attacks were first reported early Tuesday morning in Ukraine, where banks, an airport and the metro system, among other systems, were affected. It quickly spread to other European countries and the U.S. Some say the current attack is a variant of Petya, malware that has the ability to quickly spread over networks.