Cybersecurity firm CrowdStrike – whose faulty security update caused a “blue screen of death” on thousands of Windows computers around the world – claimed that a “significant number” of systems affected by the digital blackout have now been brought back online.

In a social media post, the company added that it “continues to focus on restoring all systems” and said it is developing a new fix that it hopes will speed the recovery of the remaining computer systems.

Microsoft has estimated that the incident, described as one of the worst digital crashes in history, affected 8.5 million computers worldwide.

Businesses, banks, hospitals and airlines were among the worst affected and many are still struggling to fully restore their systems.

CrowdStrike did not say how many devices are still affected by the problem.

“We understand the profound impact this has had on everyone. We know our customers, our partners and their IT teams have been working tirelessly and we are deeply grateful,” CrowdStrike said. “We apologize for the disruption this has caused.”

The massive outage brought into focus the vulnerability of global computer networks, showing how a single glitch can cause global chaos.

“Too often these days, a single glitch leads to an entire system going down, affecting industries from health care and airlines to banks and car dealers,” US Federal Trade Commission chairwoman Lina Hahn said in a social media post. “These incidents reveal how concentration can create fragile systems.”