This paper describes the proposal for a verification mechanism that takes advantage of UEFI BIOS resources to attest the integrity of the software of embedded systems used in IoT. This mechanism is composed by an integrity verification application called AVIS UEFI, which is executed in the Pre-Boot Applications phase and uses digital signature and keys stored in cryptographic devices to verify if the software has been tampered with. According to the result of the verification, the system is initialized or shut down. The next steps of this work will be to finalize the implementation of the prototype, present and evaluate the test results to show its applicability in a real scenario.