In one episode, there was a story about how electronic voting machines were manipulated by rogue software that created confirmation of the vote cast for the voter but a false record for counting.
So it amused me to find this today in which different (obviously) software is being used to a very similar end. https://www.mynewsdesk.com/uk/hm-revenue-customs-hmrc/pressreleases/hmr…
Succinctly, software installed in electronic tills produces an accurate record for the customer but diverts information relating to some sales to a hidden ledger and effects payment by crediting an account outside the jurisdiction. Apparently, the software is in quite widespread use.
In principle, it's no different to businesses operating two sets of books or, even, a till and a cash drawer but in practice it means that the fraud is hidden from staff because what they see is what the customer sees and that is what everyone expects to see.