美国政府报告突出电脑黑客严重威胁美国经济

U.S. officials say a new government report details the threat hackers pose to the nation's economy, with China a clear leader among countries carrying out cyber attacks.

Officials have described the classified "National Intelligence Estimate" to U.S. media, including The Washington Post, which said late Sunday hackers are targeting the energy, finance, information technology, aerospace and automotive sectors.

Some estimates put the cost to the U.S. economy at tens of billions of dollars each year.  But, with some companies reluctant to report when they are hacked, the true cost is not known.

The White House is weighing how to respond, with options including possible trade actions and visa restrictions.  The Washington Post says President Barack Obama is expected to issue an executive order on cyber security this week aimed at helping the private sector protect against hacking attempts.