South Korean banks wary after cyberattack claim by hackers

Armada Collective, the claimant group has threatened to carry out a distributed denial-of-service (DDoS) attack if the demanded money is not paid by June 26, South Korean news agency Yonhap reported on Thursday.

Among those affected are the country's three largest banks - KB Kookmin Bank, Shinhan Bank and Woori Bank - and others, such as KEB Hana and NH Bank, according to South Korea's financial authorities.

The banks have boosted their security systems in the face of a possible attack that could disrupt their websites. The Armada Collective has also threatened other companies in the past with such attacks, demanding payments in the bitcoin cryptocurrency.