Counterfeit electronics in "America's most crucial weapons systems." Senator Carl Levin. China denies visit.

U.S. Senators staffs have asked to visit notorious China counterfeiting sites in Shenzen, but have been denied visas by the Chinese government.

And one of those Senators, Carl Levin, has stated what most in the industry have long known: counterfeit microchips and other electronics have infiltrated the U.S. most crucial weapons systems.

"Counterfeit microprocessors …were purchased by the Air Force for use on the F-15 operational flight control computers, " Levin said, adding tht counterfeit microcircuits have been found on Missile Defense Agency hardware.

The attempted trip to Shenzen, and the blunt statements come as Levin and John McCain, co-chairpersons of the Senate Armed Services Committee, continue an investigation into the infiltration of counterfeit parts in the military supply chain. This investigation coincides with a greatly heightened awareness of cyberwarfare threats, which typically exploit counterfeit, vulnerable, or sabotaged electronics.

Even if the Chinese end up granting visas to the senators, they don't want to make the investigation easy, the senators said. "The Chinese have said, 'Well, even if this could be arranged, there would have to be a Chinese official present during the interviews.' That is a nonstarter," Sen. Carl Levin. D-Michigan, said. "We do not have somebody looking at our staff while they're interviewing people who are relevant to an investigation."

The dramatic turn in the investigation comes as new warnings about cyberwarfare are issued by government and private security experts. Cited as the top security threat in 2011, cyberwarfare became shockingly visible with the success of Stuxnet virus, which hit and disabled nuclear reactors in Iran, in 2009 and 2010. (see our post)

Stuxnet showed that defective, vulnerable or sabotaged hardware can be exploited by computer viruses to wreak real, physical destruction. The problem of counterfeit, and sabotaged microchips and other electronics --and the need for anti-counterfeiting measures--has never seemed so urgent.