The story spread in bond markets in New York and Asia on Monday. China, according to a rumor that circulated largely via social media, was "massing" 150,000 troops on its border with North Korea. The timing of the alleged troop movements, coupled with reports of possible U.S.-China discussions of what to do about Pyongyang’s nuclear arsenal, was cited by analysts as one reason interest rates on bonds were creeping up.

Was there any substance to the rumor? Not according to senior U.S. military and intelligence officials. There was no "massing." As many as 250,000 Chinese troops are always operating in northeastern China, and the U.S. did not see any sign Beijing had moved them closer to the Yalu River, which separates North Korea from China. 

Financial analysts were not surprised. Fake financial news has a longer history that any other kind of false reporting. Some people repeat rumors because they believe them to be fact. Others, however, may be tempted by the knowledge that "news" of impending doom can move markets. There is money to be made before the news is proven true or false. The advent of social media and high-speed trading just adds to the possibilities.

One Pentagon official told NBC News, in language too profane to publish, that that's exactly what he thought happened with the China troop tale.