If you enjoyed the video about anti-counterfeiting measures on bank notes, you might like this video here about the EURion Constellation, a somewhat secretive series of rings seen on many bank notes worldwide that tell a computer that what it's looking at is currency. It is just one of the many ways a copy machine or computer application prevents copying or altering of a bank note.
HP Labs' Steve Simske is an Honorary Professor at the University of Nottingham and here he explains the nerdy side of anti-counterfeiting inks and printing methods. As with most videos from the Computerphile YouTube channel, the videos here are a bit technical but incredibly fascinating if you can sit through the jargon to realize how much brains and smarts go into something as simple as printing.
Here's an enlightening short documentary from VICE about the growing counterfeit money market in Lima, Peru. The country has taken the counterfeit crown from Colombia by producing what the US considers to be the best counterfeit notes in the world. For just a few cents per note (usually in $20s, $50s, or $100s) and the right amount of contacts, you could potentially snag yourself thousands in money that could pass in most places in the US. It's kind of scary to think about how many of these notes have flooded the US in circulation already. Have I accidentally used one of these? Who knows. But it's bad news for US buyers either way.