"We can confirm that Maersk IT systems are down across multiple sites and business units. We are currently assessing the situation," Moller-Maersk tweeted. "Global cyber-attack Petya is affecting multiple businesses. We are responding to limit impact on customers and to uphold operations. Update to follow."
The malware, called Petya, was first identified in March 2016. Security researchers said on Tuesday that it appears to be spreading on the same exploit as the WannaCry ransomware that took down hundreds of thousands of computers worldwide last month.
Ukrainian government agencies, banks and electrical companies have also been affected, as well as Russia's oil company Rosneft and dozens of other companies across the United Kingdom, France, Spain and other nations.
Moller-Maersk handles one out of every seven containers shipped globally, according to published reports.