An apparently sophisticated and coordinated cyber attack has caused widespread disruption to computer networks and three of South Koreas largest broadcasters and two of the country’s banks.

The attack first showed itself at 2pm on Wednesday when computers at KBS, MBC and YTN shutdown. Upon restarting, the computers displayed error messages saying they were unable to boot. Apparently the boot record or entire operating system has been removed from the computers.

KBS broadcast images of computers in its offices showing an error screen and one KBS employee posted a picture of his laptop screen on Twitter (right.)

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