A ransomware attack over the weekend could have affected as many as 200 companies.

The victim of the attack was the Miami-based IT management firm Kaseya. Kaseya's software is used by a large number of US businesses, any of which could now be affected. 

"This is a colossal and devastating supply chain attack," said John Hammond, of the cybersecurity firm Huntress, in an email to The Guardian. "It has the potential to spread to any size or scale business."

At least one business outside the US has also been affected. The Swedish supermarket chain Coop was forced to close the majority of its 800 stores in the country after the attack knocked out its cash register systems.

The hacker group REvil is suspected of being behind the attack. REvil threatened Apple and its subcontractor Quanta Computer back in April, saying that unless it was paid a ransom it would publish stolen drawings of future products, including a MacBook Pro. This is something we previously reported on.

The hacker group demanded $50m (roughly £36m) from Quanta Computer, writes AppleInsider, but it is unknown how much was demanded from Apple or if any money was paid out.

This article originally appeared on Macworld Sweden. Translation and additional reporting by David Price.