Hospitals, major companies and government offices have been hit by a massive wave of cyberattacks across the globe that seize control of computers until the victims pay a ransom.
Cybersecurity firm Avast
said it had identified more than 75,000 ransomware attacks in 99 countries, making it one of the broadest and most damaging cyberattacks in history.
Avast said the majority of the attacks targeted Russia, Ukraine and Taiwan. But U.K. hospitals, Chinese universities and global firms like Fedex (
FDX) also reported they had come under assault.
Europol said Saturday that the attack was of an "unprecedented level and requires international investigation."
The ransomware, called "WannaCry," locks down all the files on an infected computer and asks the computer's administrator to pay in order to regain control of them. The exploit was leaked last month as part of a trove of
NSA spy tools.
The ransomware is spread by taking advantage of a Windows vulnerability that Microsoft (
MSFT,
Tech30) released a security
patch for in March. But computers and networks that hadn't updated their systems were still at risk.
In the wake of the attack, Microsoft said it had taken the "highly unusual step" of releasing a patch for computers running older operating systems including Windows XP, Windows 8 and Windows Server 2003.
"Affected machines have six hours to pay up and every few hours the ransom goes up," said Kurt Baumgartner, the principal security researcher at security firm Kaspersky Lab. "Most folks that have paid up appear to have paid the initial $300 in the first few hours."