It seems like they just changed the $100 bill, but today the U.S. Government announced it's been redesigned again, bringing in 3D technology to make it even harder to counterfeit. Try copying this, bad guys: That blue stripe is called a 3D security ribbon, and it contains a double image of the numeral 100 and bells that alternate as you tilt the bill.
Check out that copper-colored inkwell to the right of the blue stripe, which changes color as you tilt it, making the bell pictured inside appear and disappear as you move the bill around. The Treasury Department has been researching these neat tricks for a decade, trying to find a bill that's impossible to duplicate but easy to immediately recognize as genuine.
Looks like the Feds nailed it this time. Those new tricks are added to the old ones they kept in the design, including a watermark portrait of Benjamin Franklin, a tiny security thread, and that color shifting numeral 100.
When will we see this new currency? So far, all the government is saying is "TBD," to be determined (update: now they tell us — February 10, 2011). Great. Just when they create the perfect $100 bill that's impossible to duplicate, thieves are moving on, now figuring how to crack our financial system in the cloud. Perfect timing, guys.