AFP, Paris

Hundreds of Swedish supermarkets remained shut yesterday after a major cyberattack that has crippled hundreds of companies worldwide for the past four days, with the perpetrators demanding $70 million in bitcoin to undo the damage.

Kaseya, the Miami-based IT company at the centre of the hack, said late Monday that up to 1,500 businesses had been affected by Friday’s attack, which has been blamed on Russian-speaking hackers.

Experts believe this could be the biggest “ransomware” attack on record -- an increasingly lucrative form of digital hostage-taking in which hackers encrypt victims’ data and then demand money for restored access.

The Kaseya attack has ricocheted around the world, affecting businesses from pharmacies to gas stations in at least 17 countries. Kaseya provides IT services to some 40,000 businesses globally.

REvil, a group of Russian-speaking hackers who are prolific perpetrators of ransomware attacks, are believed to be behind Friday’s assault. A post on Happy Blog, a site on the dark web associated with the group, claimed responsibility for the attack, saying it had infected “more than a million systems”.

The group was responsible for around 29 percent of ransomware attacks in 2020, according to IBM’s Security X-Force unit, looting an estimated $123 million.