In a note accompanying the company's interim report for the second financial quarter of 2017, chief executive Søren Skou said: "In the last week of the quarter we were hit by a cyber attack, which mainly impacted Maersk Line, APM Terminals and Damco.
"Business volumes were negatively affected for a couple of weeks in July and as a consequence, our Q3 results will be impacted. We expect that the cyber attack will impact results negatively by USD 200-300m."
Maersk is a Danish business conglomerate that operates in the transport and logistics, and energy sectors. It has been the largest container ship and supply vessel operator since 1996.
It began in Europe and then spread to other regions, encrypting files on Windows machines and demanding 100 bitcoin for decrypting the same.
At the time it said: "We can confirm that Maersk has been hit as part of a global cyber attack named Petya on the 27 June 2017. IT systems are down across multiple sites and select business units.
"We have contained the issue and are working on a technical recovery plan with key IT-partners and global cyber security agencies.
"We have shut down a number of systems to help contain the issue. At this point our entities Maersk Oil, Maersk Drilling, Maersk Supply Services, Maersk Tankers, Maersk Training, Svitzer and MCI are not operationally affected. Precautionary measures have been taken to ensure continued operations.
"Maersk Line vessels are manoeuvrable, able to communicate and crews are safe. APM Terminals is impacted in a number of ports."
CNBC quoted the company as saying on Tuesday: "This cyber attack was a previously unseen type of malware, and updates and patches applied to both the Windows systems and anti-virus were not an effective protection in this case.
"In response to this new type of malware, A.P. Moller Maersk has put in place different and further protective measures and is continuing to review its systems to defend against attacks."