urrency often changes over time to combat counterfeiting technologies by keeping the latest bills fresh with difficult to duplicate features. Regardless of the Secret Service and the Bureau of Printing and Engraving's efforts, supernotes continue to flourish internationally. A supernote is a counterfeit, high value bill of such quality that it is virtually indistinguishable from the original even under scrutiny. Even the latest batch of 2003 series, $100 dollar bills have been found circulating through currency exchanges. According the congressmen that oversaw the Secret Service's anti-counterfeit operation, "it’s by far the most sophisticated counterfeiting operation in the world ... We are not certain as to how this is being done or how it’s happening." Rumors of the supernote operation include the long standing belief the Chinese and North Koreans produce them. Others implicate a secret CIA printing press used to fund operations outside of congress' knowledge.