South Korea is experiencing a third wave of suspected cyber-attacks designed to paralyse a number of major websites. The White House and the Pentagon were targeted earlier this week.
The BBC reports one of the country's biggest banks, a national newspaper and the South Korean spy agency appear to have been targeted.
Some reports suggest the attacks might be the work of North Korea.
There were similar attacks earlier in the week in South Korea and the United States, with the White House and the Pentagon targeted.
In what is known as a "denial of service" attack, thousands of virus-infected computers are hijacked and simultaneously directed to a particular site, overwhelming it with the sheer volume of traffic.
A third wave of attacks is now reported to be underway.
South Korea has announced that it will speed up plans for a cyber warfare unit to counter such threats.