Advances in technology have created some of the most sophisticated, counterfeit-proof currencies in history. However, these same leaps in technology keep counterfeiters fast on the trail of the latest wave of security improvements and attempts to keep the counterfeiters at bay.

Mighty Greenback
American currency is among the most popular in the world. Despite some recent setbacks, the mighty Greenback is still seen as the most secure store of value and is circulated more outside of the U.S. than inside its borders. One estimate detailed that more than 75% of the nearly $600 billion in $100 bills circulates outside of the U.S. Due to its popularity, the American $100 bill is one of the most counterfeited currencies, but also one of the most difficult to fake.

A slideshow on the website popsci.com from a couple of years ago interviewed a convicted counterfeiter about his thoughts on the integrity of the U.S. dollar. The slideshow illustrates the sophistication of the technologies to protect the bills, but points out a number of weaknesses that counterfeiters look to exploit. For instance, counterfeiters can replicate color-changing ink by mixing glitter in a blender. They can also use high-quality printers and scanners to assist in copying hard-to-create images. Another common counterfeiting scheme is to remove the watermark from a $100 bill and affix it to a $5 bill, since both bills use the same image. Small images are also easily copied, as are security threads, though the Federal Reserve has plans to embed even more images to stay ahead of the game.

Best of the Best
Each year, the International Association of Currency Affairs (IACA) holds an awards ceremony for currencies and individuals that have made great leaps in protecting the integrity of currencies and the technologies that go into creating and manufacturing them. In 2011, the IACA voted the Bank of Uganda as the winner of the best new banknote.

The Bank of Uganda highlighted the first major redesign in more than two decades and added security features. The bank noted security features that are both visible as well as hidden within the notes. These features include raised printing, serial numbers, watermarks and a security thread that is inside the note and has the denomination printed on it. The currency also has certain "iridescent" features that are visible when the note is held at an angle. Some of the runner-ups for 2011's best new banknote were the Philippines Central Bank and the Central Bank of Sri Lanka. Scotland's Clydesdale Bank won the award in 2010.

The IACA also gave awards for important new security features. Among the more interesting advancements in security were holograms that detailed "depth and movement," and pixel watermarks with a three-dimensional look that could change based on angle and lighting. The most counterfeit-proof currencies are ones that combine the latest technology with features that are difficult to fake. America, Kazakhstan, Mexico, Sweden and Hong Kong were said to have the most difficult-to-fake currencies in 2011.

The Bottom Line
The IACA awards provide some of the best insight into the currencies and technologies that deter counterfeiting. Money may never become counterfeit-proof, but these security advancements should make some currency thieves rethink their careers, as it might be more profitable for them to devote their energy and attention to earning money legally.