According to Wikipedia, the company, founded in 1983 and originally owned by South Korean giant Hyundai, was merged with SK Group, the third largest conglomerate in South Korea, in 2012.
In 2018, SK hynix earned revenue of US$35.27 (A$49 billion). The company is also the the third biggest manufacturer of semiconductors in the world.
The criminals who staged the attack have released a bunch of documents (screenshot below) which appear to be from hynix.
There are also a number of files relating to Paul Cho who was general counsel at Hynix from 2014 to 2019.
Contacted for comment, a SK hynix spokesperson told iTWire that the company had no official statement to make right now.
The Maze ransomware has been used by a large number of groups to attack various companies this year. Among attacks of note have been those on the global technology firm Pitney Bowes, Texas foundry group X-FAB, a Thailand power authority, the Belgian accounting firm HLB, the global defence group ST Engineering and the Sydney strata management company Strata Plus.
Also attacked with the same ransomware have been South Korean electronics giant LG, the Thai Beverage Public Company, Japanese multinational optical and imaging products vendor Canon and Indian sweets maker Haldiram's.