It is possible to highlight the main features of genuine banknotes:
By means of water drops. If from this image greased, then it is a fake on an inkjet printer.
Must be translucent watermark.
Should be security threads. Sometimes they have to change with the lumen.
The combination of numbers to the light. Sometimes the numbers are changed when candled at others.
An image on a banknote, visible only in transmitted light.
Paint that when you change the angle of view changes color
Labels for the visually impaired.
P. S. There are secret features which are known only to the national banks.
Features authentic banknotes may vary from its nominal value and the country.