The virus, which demanded a payment worth $300 as it locked up files at companies and government agencies including the Chernobyl nuclear site, appeared similar to the WannaCry ransom ware that swept the world last month, hitting more than 200 000 users in more than 150 countries.
But the new attack appeared much smaller in scale, with global cyber security firm Kaspersky Lab estimating the number of victims at 2 000. There was no immediate indication of who was responsible.
Some IT specialists identified the newcomer as “Petrwrap”, a modified version of ransom ware called Petya which circulated last year. But Kaspersky described it as a new form of ransom ware.
The government of Ukraine, where the attacks were first reported and appeared most severe, said the attack had been halted, but key organisations were still reporting problems.
