Special types of paper , safety yarns and sophisticated printing techniques are used to prevent paper money from being easily counterfeited . Money is fake or real , it can be caught by examining it with the naked eye. Even the visually impaired can catch the original-fake by touching the high-low design in the corner of the note. But even after that, all the subtle ways to counterfeit money using modern technology have come out that it is difficult to understand the difference just by looking at it with the naked eye. Apart from that, if a lot of money is transacted together, it is time to check the notes one by one. So the machine has note testing system. But how the machine catches counterfeit notes is kept secret. Once it is known, the fraudsters will come up with a strategy to forge notes by evading the machine. Nonetheless , machines typically use at least two techniques. These are perceived by light rays or perceived in a magnetic manner. Paper note printing ink has some magnetic properties , the presence of which is perceived by the machine. By analyzing the precise chart of the electronic signature on the note , the computer can tell whether it is real or fake . So even if the photocopy is done in a sophisticated way, the machine catches the counterfeit notes. In the second method, a ray of light is thrown on the note. Some note inks absorb that light, while others reflect light. By checking the results , the computer can understand whether the note is genuine or counterfeit. In both cases the test takes about one second. Some countries use polymer notes instead of paper to stop counterfeiting. These notes cannot be easily photocopied. There are some additional security signs in those notes. But even though it is difficult, polymer notes are also counterfeit , although the rate of counterfeiting is low. However, the machine can now identify those counterfeit notes.