A large-scale cyberattack, believed to have been implemented with malicious software stolen from the National Security Agency, caused chaos in hospitals and government institutions in nearly 100 countries on Friday. The attack was first reported in the United Kingdom, where British authorities said hospitals were forced to send patients away. Late Friday, dozens of other countries reported falling victim to the same cyberattack. The attack targeted hospitals, educational institutions, and government institutions by locking computers and demanding a ransom of between $300 and $400 to restore access, Reuters reported. Hackers carried out the attack by tricking people into opening malicious software disguised as work invoices, job offers, security warnings and other seemingly important emails. Anti-virus maker Avast said they had recorded 57,000 infections in 99 countries, including countries in Africa, Latin America, and Asia. Russia and Ukraine were reported to be among the hardest hit by the attack. China reported that several of its educational institutions came under attack, while South Korea said it was aware of a university hospital being affected. In Russia, the attack hit the Interior Ministry and the Emergency Situations Ministry, as well as Sberbank, the country’s largest bank. Experts say the full extent of the damage may not be felt until Monday, because some companies and institutions may not yet be aware of the attack.