Published: 2017-05-15 21:56:40 BdST
Cyber security experts said the spread of the worm dubbed WannaCry - "ransomware" that locked up more than 200,000 computers in more than 150 countries - had slowed but that the respite might only be brief amid fears new versions of the worm will strike.
In a blog post on Sunday, Microsoft President Brad Smith appeared to tacitly acknowledge what researchers had already widely concluded: The ransomware attack leveraged a hacking tool, built by the US National Security Agency, that leaked online in April.
"This is an emerging pattern in 2017," Smith wrote. "We have seen vulnerabilities stored by the CIA show up on WikiLeaks, and now this vulnerability stolen from the NSA has affected customers around the world."
He also poured fuel on a long-running debate over how government intelligence services should balance their desire to keep software flaws secret - in order to conduct espionage and cyber warfare - against sharing those flaws with technology companies to better secure the internet.
"This attack provides yet another example of why the stockpiling of vulnerabilities by governments is such a problem," Smith wrote. He added that governments around the world should "treat this attack as a wake-up call" and "consider the damage to civilians that comes from hoarding these vulnerabilities and the use of these exploits."
The NSA and White House did not immediately respond to requests for comment about the Microsoft statement.
Economic experts offered differing views on how much the attack, and associated computer outages, would cost businesses and governments.
The non-profit US Cyber Consequences Unit research institute estimated that total losses would range in the hundreds of millions of dollars, but not exceed $1 billion.
Most victims were quickly able to recover infected systems with backups, said the group's chief economist, Scott Borg.
California-based cyber risk modelling firm Cyence put the total economic damage at $4 billion, citing costs associated with businesses interruption.
US President Donald Trump on Friday night ordered his homeland security adviser, Tom Bossert, to convene an "emergency meeting" to assess the threat posed by the global attack, a senior administration official told Reuters.
Senior US security officials held another meeting in the White House Situation Room on Saturday, and the FBI and the NSA were working to help mitigate damage and identify the perpetrators of the massive cyber attack, said the official, who spoke on condition of anonymity to discuss internal deliberations.
The investigations into the attack were in the early stages, however, and attribution for cyber attacks is notoriously difficult.
The original attack lost momentum late on Friday after a security researcher took control of a server connected to the outbreak, which crippled a feature that caused the malware to rapidly spread across infected networks.