The impact of this weekend's "ransomware" attack is still spreading as companies and government agencies worldwide turn on their computers for the work week.
The Chinese government says nearly 30,000 of its institutions have been affected, including universities, mail delivery services, hospitals and shopping malls.
A smaller number of computers were infected in Japan and South Korea, where officials say security updates helped contain the damage.
The initial cyberattack on Friday hit tens of thousands of victims across 150 countries, including Britain's hospital system and Germany's national railway.
The virus exploits a vulnerability in Microsoft Windows and locks a user's computer until a ransom is paid.
Cyber experts are urging organizations and companies to immediately update older Microsoft operating systems like Windows XP with a patch released by Microsoft.
It's still not clear who was behind the attack.