A new ransomware exploit dubbed "Petya" struck major companies and infrastructure sites this week, following last month's WannaCry ransomware attack, which wreaked havoc on more than 300,000 computers across the globe. Petya is believed to be linked to the same set of hacking tools as WannaCry. Petya already has taken thousands of computers hostage, impacting companies and installations ranging from Ukraine to the U.S. to India. It has impacted a Ukrainian international airport, and multinational shipping, legal and advertising firms.