Friday's attack, believed to the biggest of its kind ever recorded, locked up computers and held users' files for ransom at a multitude of hospitals, companies and government agencies.
The malicious software behind the onslaught appeared to exploit a vulnerability in Microsoft Windows that was supposedly identified by the National Security Agency for its own intelligence-gathering purposes and was later leaked to the Internet.
Britain's national health service fell victim, its hospitals forced to close wards and emergency rooms and turn away patients. Russia appeared to be the hardest hit, according to security experts, with the country's Interior Ministry confirming it was struck.
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All told, several cybersecurity firms said they had identified the malicious software responsible for tens of thousands of attacks in more than 60 countries, including the United States, though its effects in the U.S. did not appear to be widespread, at least in the initial hours.
Ransomware is software that freezes up a machine and flashes a message demanding payment to release the user's data. In the U.S., FedEx reported that its Windows computers were "experiencing interference" from malware, but wouldn't say if it had been hit by ransomware.
Microsoft released a patch in March that addresses this specific vulnerability, and installing this patch will help secure systems from the threat. Individual users are often the first line of defense against this and other threats, DHS said.
DHS urges all PC users to update their operating systems and "implement vigorous cybersecurity practices at home, work, and school."
HOW TO KEEP YOUR SYSTEM SECURE:
- Update your systems to include the latest patches and software updates.
- Do not click on or download unfamiliar links or files in emails.
- Back up your data to prevent possible loss, whether you are at a home, work, or school computer.
Find more cybersafety tips from DHS here.
The Associated Press contributed to this report.
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