There are several levels at which hardware wallets can be attacked, Bakkum explained in his presentation, which repeated points made in a company blog post from October: Attacks on the communication layer (meaning, the protocol connecting a wallet to a laptop, be it USB port, QR code or SD card, is compromised), the logic layer (malicious software is injected) and physical layer (attacker breaks open the device, attach probes and tampers with it).
Air Gap? Hardware Wallet? Multisig?
