While the security experts have struggled to find the so-called "patient zero" in the attack, they have been more successful in finding the cause of the attacks and the reason why it was so successful.
Window XP, Windows Vista users are particularly at risk because some of these users might not have licensed version of the software, or might not have updated their computer.
The term ransomware refers to malicious software that infects or locks a computer, preventing access to files.
There are fears of further "ransomware" attacks as people return to work on Monday. Here's a quick look.
"More action is needed, and it's needed now", he said.
Sometimes, hackers might attack backups themselves.
Wannacry came about because of a leak of NSA secrets, including a flaw in older Windows systems called Eternalblue. Most of the times, operating systems have certain vulnerabilities, but they are discovered and receive updates which should fix them.
Microsoft rolled out over the weekend a patch for Windows XP, Windows Server 2003 and Windows 8, which are operating systems for which it no longer provides mainstream support.
"This attack demonstrates the degree to which cybersecurity has become a shared responsibility between tech companies and customers", Smith said. "Customers should use vigilance when opening documents from untrusted or unknown sources". "We have seen vulnerabilities stored by the Central Intelligence Agency show up on WikiLeaks, and now this vulnerability stolen from the NSA has affected customers around the world", Smith wrote.
A hacker group - known as Shadow Brokers - obtained an arsenal of cyber warfare tools in April from the NSA, of which the USA agency called "Eternal Blue".
"We are closely monitoring the situation and have instructed the banks' local information technology teams to keep a watch on the systems in branches". Users might not be able to do much here.
The WannaCrypt exploits used in the attack were drawn from the exploits stolen from the National Security Agency, or NSA, in the United States. Microsoft had released an update to fill the vulnerability the month before, apparently identifying the hole on its own. According to reports, the companies investing in Bitcoin has increased during the past week following the latest incident targeting out-of-date Windows-powered IT infrastructure.
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