Fred Voccola, the Florida-based company's CEO, said in an interview that it was hard to estimate the precise impact of Friday's attack because those hit were mainly customers of Kaseya's customers.

Kaseya is a company which provides software tools to IT outsourcing shops: companies that typically handle back-office work for companies too small or modestly resourced to have their own tech departments.

One of those tools was subverted on Friday, allowing the hackers to paralyze hundreds of businesses on all five continents. Although most of those affected have been small concerns - like dentists' offices or accountants - the disruption has been felt more keenly in Sweden, where hundreds of supermarkets had to close because their cash registers were inoperative, or New Zealand, where schools and kindergartens were knocked offline.