Vital data components of a computer system are protected by a mechanism for detecting unauthorized alteration, preferably in the form of digital signatures to detect unauthorized alteration. A vital data validation mechanism is provided to verify that vital data modules have not been tampered with. The vital data validation mechanism verifies the current state of each vital data module, preferably by decrypting the digital signature. The validation mechanism also checks an alteration log to verify that no alterations have been made to the corresponding memory locations. The second verification is intended to detect whether a vital data module has been altered temporarily, and then restored to its initial state.