SEOUL - Three South Korean broadcasters and two banks were hit by a major cyber attack this afternoon, in an apparently successful attack that has rendered system-wide computer networks unusable since 1400KST (0100EST).

KBS, MBC and YTN were all hit by the attack, as were Shinhan and Nonghyup banks, South Korean news agency Yonhap reported. KBS staff member Luke Cleary tweeted a picture of his laptop screen, apparently showing a wiped operating system: