In the wake of last month’s WannaCry malware outbreak, Microsoft on Tuesday released security updates for older versions of Windows, reported The Guardian.

WannaCry is a malicious software that had crippled systems worldwide and affected more than 99 countries in a cyber attack in May. It had locked data on computers it struck, which could only be released after a paying a ransom in bitcoins.

The patches will include updates to Windows XP, which was the operating system targeted by the ransomware in May. Microsoft usually offers updates to the operating systems that are still supported, meaning Windows 7 and newer. However, Adrienne Hall, the head of Microsoft’s Cyber Defense Operations Center, said the elevated risk of destructive cyber-attacks at this time was very high.

“We made the decision to take this action because applying these updates provides further protection against potential attacks with characteristics similar to WannaCrypt [alternative name to WannaCry],” she said.

The new patches will fix 16 vulnerabilities, out of which 15 are listed as critical by Microsoft.

The Shadow Brokers, a hacking group believed to be behind a massive dump of National Security Agency cyber-weapons and software, were responsible for releasing the vulnerability. This had led to WannaCry being able to replicate itself and causing massive damage internationally. The vulnerability was referred to by the NSA as “EternalBlue”.

WannaCry had hit hundreds of thousands of systems across the world. The major cyber attack had targeted several nations, bringing operations at hospitals, telecommunications firms and other companies to a halt.