The unprecedented attack forced workers to improvise with Twitter, WhatsApp and Post-It notes as they struggled to get goods moving from ships to shore again, the company said.

The crisis put Maersk in uncharted territory. It responded as best it could, but “there’s no benchmark for this,” company spokeswoman Katherine Mosquera said. “Is it good? is it bad? We don’t know. It happened.”

Maersk’s revelations were part of an interim second-quarter earnings report in which the Copenhagen-based global transport and energy company gave investors a preview of expected costs from the malware attack. The worm, dubbed NotPetya, locked access to systems that Maersk uses to operate shipping terminals all over the world and took two weeks to fix.

The company said the attack is expected to dampen its third-quarter results, but not enough to overshadow a generally good performance due to improving global economic conditions.

NotPetya, which has been traced to compromised tax-accounting software widely used in Ukraine, began spreading in late June, a few weeks after a similar ransomware attack called WannaCry seized computers in British health clinics. Like WannaCry, NotPetya exploited a vulnerability in unpatched Microsoft Windows operating systems and relied on a break-in technique that may have been stolen from the U.S. National Security Agency.

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