(SEOUL, South Korea) -- A cyber attack crippled computer networks at TV stations and major banks in South Korea on Wednesday, prompting a police investigation.
When users tried to open their individual computers, they said they saw three skulls on a black screen with the phrase "hacked by whoisteam." Some experts told ABC News that simply represents an unknown secretive group of hackers.
There's speculation that the attack originated from North Korea. Last week, Pyongyong had blamed the U.S. and South Korea for shutting down their websites.
Systems at the South Korean military have not been affected but the army has raised its defense level.
Copyright 2013 ABC News Radio