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>Like previous ransomware, the attack spreads by phishing emails,[16] but also can infect directly across a network any exposed systems which have not installed recent security updates[5][17] by using the EternalBlue exploit developed by the U.S. National Security Agency (NSA).[18][19] Although a "critical" patch to remove the underlying vulnerability for supported systems had been issued by Microsoft on 14 March 2017,[20] many organizations had not yet applied this.[21]
Thanks America