For as long as we’ve had banknotes we’ve had people determined to find messages hidden in their design. While most of these are rightly dismissed as paranoia, however, there is at least one series of symbols that can be found on currency from all across the world – though its meaning has more to do with security that conspiracy.

If you examine a note closely – no matter where it comes from – you should be able to spot this particular pattern of circles. Sometimes it’s out in the open and sometimes it’s hidden as part of the greater design, but it’ll always be there somewhere.

This particular pattern is known as the EURion constellation, and was first found on a €10 note in early 2002. Since then it’s been spotted on currencies ranging from the Aruban florin to the mighty US dollar, where it plays a role in combating counterfeiting efforts.

After all, despite the huge array of special dyes, polymers and watermarks they use, at the end of the day a banknote is still a piece of paper. As high-quality laser printers and image editing software become more and more accessible, this naturally presents a few problems.

But if you were to head over to a photocopier right now and try to whip up a few copies from the cash in your pocket – something that you definitely should not do, by the way – you would find that the device simply refuses to work.

Similarly, if you track down an image of a note and try to open it up in Photoshop or another editing programme, it will almost certainly spit out a message warning that you’re in danger of breaking the law and lock up.

In both cases the software has been programmed to recognise hidden codes woven into the designs. The exact details of how this works are hard to find – governments and banks are naturally rather hesitant to reveal the details of their anti-counterfeiting measures after all – but the EURion constellation is the first line of defence in keeping casual criminals at bay.

It’s thought that the pattern is specifically designed to stop notes from being photocopied rather than scanned or edited. The pattern is a relatively simple countermeasure that’s prominent enough to be picked out by the human eye, so determined criminals could probably work around given enough time.

What is highly effective at, however, is putting a stop to the curious and the desperate – people who may give counterfeiting a try as a prank or because they don’t realise quite how serious a crime they’re committing.

It’s thought that there are much more sophisticated symbols and codes that Photoshop and other computer software can pick up on, as they tend to reject images even when the EURion sections are hidden.

Adobe, who owns Photoshop, says that it uses a system designed by the Central Bank Counterfeit Deterrence Group, though it’s rather tight-lipped when it comes to revealing any details..