A U.S. defense official says North Korea was behind the cyber attacks that targeted dozens of Web sites in South Korea and the United States this week.

The unnamed Pentagon official told Fox News Wednesday that the series of attacks did not penetrate the Department of Defense's computer systems.

According to the report, some defense officials complained privately that the Pentagon wasn’t informed about the attacks from the Department of Homeland Security, which is responsible for protecting government sites from cyber attacks, and instead found out about the attacks from the media.

At the State Department, spokesman Ian Kelly said the ministry is investigating the series of cyber attacks but has yet to confirm their source.