At least three U.S. oil companies were hit by cyberattacks that may have come from China, according to a Christian Science Monitor report.

"The attacks occurred in 2008, and were directed at Marathon Oil, ExxonMobil, and ConocoPhillips," writes Computerworld's Jaikumar Vijayan.

"The attacks, which have been a closely guarded secret of oil companies and federal authorities, were aimed at extracting 'bid data,' or information detailing the quantity, value and location of oil resources," Vijayan writes.

Click here to read the Computerworld story.