You hear about the hardware crypto wallets with sim cards in them that read the pincode off the displays? That was a slick as shit supply chain attack:

https://www.theverge.com/tech/1009294/ledger-wallet-tampering-suspected-after-reports-of-crypto-thefts

The intial wallets discovered has crude wiring soldiered on, but later ones had custom black PCBs that looked very much like they were part of the wallets circuitry unless you knew exactly what you were looking for.