A security team recently dismantled a tampered Ledger Stax unit and discovered sophisticated physical modifications. A customized sub-board had been soldered onto the mainboard, housing a Nordic nRF9151 cellular IoT chip equipped with an eSIM and a concealed antenna that supports LTE-M and NB-IoT networks.
This architecture eliminates any reliance on a connected PC or mobile device for internet access. The moment a user inputs or generates a recovery seed phrase, the rogue module captures the data and quietly transmits it via an encrypted 4G cellular connection directly to the attacker's server, turning cold storage into a self-powered listening post.
Tracing the attackers is exceptionally hard because the chip features internal secure storage that protects the host IP even under firmware reverse engineering. For crypto operations that rely on cold storage for treasury management, purchasing devices through unauthorized resellers or unverified logistics chains presents an existential operational risk.
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