OAKLAND-- -- Computer security experts are trying to track down those responsible for a wave of cyber-attacks hitting government websites and commercial websites in the United States and South Korea.

The South Korean spy agency blames North Korea for the computer attacks and says a second wave is now beginning.

The Federal Trade Commission website was down much of Monday.

But it's a different story tonight in South Korea.

When anyone tried to log on to the South Korean defense department's website on Wednesday night, nothing happened.

As Americans celebrated the country's independence on July 4th, several of the country's websites were under attack.

The problem became clear to Robert McMillan on Monday.

That's when the San Francisco computer security reporter tried to log onto the Federal Trade Commission website without success. Then he learned it wasn't just the FTC that was knocked off line, "The white house.gov website. Amazon.com. Yahoo. US bank.com, the Department of Transportation, the FAA, Secret Service."

McMilan blogged about the massive, coordinated attack that also paralyzed many South Korean government websites.

An initial investigation by South Korean officials found that many personal computers were infected with malware.. a virus ordering them to bombard major official web sites in their country and the U.S. at the same time.

U.S. officials confirmed the widespread internet assault.

"I'm comfortable that we are alert," said the chairman of the Joint Chiefs of Staff, Admiral Mike Mullen. "We recognize the probes. And we are responding."

Silicon Valley technology analyst Rob Enderle says the attack, while disruptive, was caught before any major damage was done.

And he dismisses speculation that North Korea is behind the virus. "It really didn't fit with the profile of North Korea," says Enderle. "It kinda looked like something that might have been done by overactive students or another entity. It wasn't very sophisticated."

Whoever is behind the attack, experts say it points to a new security risk.

South Korean and U.S. authorities are cooperating to track down those responsible for hijacking 12-thousand personal computers in South Korea and 8,000 abroad which they believe were exploited as vehicles for the attacks