Norsk Hydro, a Norwegian iron and steel company based in Oslo, said a March cyberattack that paralyzed its computer networks would cost the aluminum maker up to NOK 450 million ($ 52 million) in the first quarter.
The company, one of the world's largest producers of light metals, was forced to cease production on March 19 and switch to manual control after hackers blocked all its systems.
Hydro has postponed its first quarter earnings report for five weeks until June 5 from April 30 in an effort to restore its reporting system.
The company has confirmed that it has cyber insurance to cover losses from the attack.
The Norwegian State National Security Agency said the attack was carried out using a ransomware virus dubbed LockerGoga, which recodes computer files and then charges a fee to unblock them.
Hydro claims it will not pay the ransom to restore access to its computers and servers, and instead prefers to restore data from backups.
Extruded Solutions, a division of the company that turns aluminum slabs into finished products for car manufacturers and construction companies, suffered the most from the cyber attack.
"Extruded Solutions' external sales fell to 333,000 tons in the first quarter from 362,000 tons in the same quarter last year," Hydro said in a statement.
