Counterfeit United States currency

Counterfeiting of the currency of the United States is widely attempted. According to the United States Department of Treasury, an estimated $70 million in counterfeit bills are in circulation, or approximately 1 note in counterfeits for every 10,000 in genuine currency, with an upper bound of $200 million counterfeit, or 1 counterfeit per 4,000 genuine notes. However, these numbers are based on annual seizure rates on counterfeiting, and the actual stock of counterfeit money is uncertain because some counterfeit notes successfully circulate for a few transactions.
Article I, Section 8 of the U.S. Constitution gives Congress the power to "provide for the Punishment of counterfeiting the Securities and current Coin of the United States". This has been considered by federal courts to be an exception to freedom of speech.
Counterfeiting was so prevalent in the early nineteenth century that contemporary accounts like those from author John Neal claimed that as much as half of the US currency in circulation was counterfeit. By the 1830s, American newspapers began listing instructions for identifying counterfeits. Because currency was issued by individual banks, there were approximately 5,400 types of counterfeit bills in the US by the 1860s. Shortly after the Civil War, it was estimated that one third to one half of the nation's currency was counterfeit. Counterfeit money thus posed a major threat to the economy and financial system.
When the Secret Service was founded in 1865, its primary task was to minimize counterfeiting. In 2001, the U.S. Treasury estimated the prevalence of counterfeit U.S. currency in circulation at less than 0.01%.
During World War II, Nazi Germany successfully produced high-quality counterfeits of American dollar and Bank of England pound notes, although few ever were circulated thoroughly.
Superdollars, very high quality counterfeit one hundred-dollar bills, were some of the most widely distributed counterfeit American dollar bills and were still being produced after 2007. The Congressional Research Service has conducted a study and concluded with an accusation that North Korea was responsible for their production, but Pyongyang denied any involvement with Superdollar.
In 2005, Peruvian Banks ceased to accept $100 bills from the 2001 series CB-B2, due to a detection in a series of counterfeit bills in Peruvian circulation. The differences between them and genuine bills were reportedly minuscule and difficult to detect. According to Peruvian news reports, a printing plate from the Bureau of Engraving and Printing was stolen by a criminal, with possible links to al-Qaeda, and the plate was likely used to produce the counterfeit bills.
Bills forged by Anatasios Arnaouti in the UK (2005).
In recent years, metal boxes of fraudulent Federal Reserve Notes in astronomically high denominations (often in $100 million, $500 million, or $1 billion) and often with coupons attached have turned up in various Eastern countries such as the Philippines or Malaysia. In many cases, the notes are claimed to be part of a lost trove of secretly issued Federal Reserve Notes, and are special or not known to the public due to secrecy. Also, the bonds are sometimes treated to make them look old by getting them wet and moldy. However, the Federal Reserve has never issued notes in such denominations, and has issued warnings against them on its website. Additionally, there are several errors in the bonds as well as the metal boxes, many of them anachronistic. The Federal Reserve Bank of New York writes that
There have been several instances where people have used the fraudulent notes as legitimate currency, often resulting in arrest. In March 2006, agents from ICE and the Secret Service seized 250 notes, each bearing a denomination of $1,000,000,000 (one billion dollars) from a West Hollywood apartment. The suspect had previously been arrested on federal charges for attempting to smuggle more than $37,000 in currency into the U.S. following a trip to South Korea in 2002. Much of the artwork on the notes was duplicated from the real $1000 bill, including the portrait of Grover Cleveland. Another incident involving similar notes bearing a denomination each of $500,000,000, occurred in Chiasso, Switzerland, in June 2009.
In the United States, counterfeiters in small operations develop the fake currency using tools which often include printers, an iron, and green colored water. Upon collecting bills, the Federal Reserve checks all notes, destroying any whose appearance fails to fit that of a federal bill.