A method comprising: starting a pre-boot operating system upon start of a computer that controls operation of a self-service terminal (step 302); identifying any variances between a current state of the computer and data representative of a reference state within a computing environment of the pre-boot operating system (step 304), wherein the variances are identified based at least in part upon current computer configuration settings and properties including a plurality of configuration settings and properties of a platform layer system, the main operating system, data stored by the computer, devices connected to the computer, a firewall, and a threat detection program; performing at least one remedial action when any variance is identified (step 306), the at least one remedial action including: identifying a remedial data processing action to resolve an identified variance, the remedial data processing action being identified based on the identified variance; performing the remedial data processing action; re-identifying any variances between the current computer state and the data representative of the reference state; performing at least one remedial action when the verification program identifies the same or a different variance between the current computer state and the reference state; and launching the main operating system and stopping and unloading the pre-boot operating system when the verification program does not re-identify a variance between the current computer state and the reference state; and launching a main operating system and stopping and unloading the pre-boot operating system when no variance is identified (step 308). starting a pre-boot operating system upon start of a computer that controls operation of a self-service terminal (step 302); identifying any variances between a current state of the computer and data representative of a reference state within a computing environment of the pre-boot operating system (step 304), wherein the variances are identified based at least in part upon current computer configuration settings and properties including a plurality of configuration settings and properties of a platform layer system, the main operating system, data stored by the computer, devices connected to the computer, a firewall, and a threat detection program; performing at least one remedial action when any variance is identified (step 306), the at least one remedial action including: identifying a remedial data processing action to resolve an identified variance, the remedial data processing action being identified based on the identified variance; performing the remedial data processing action; re-identifying any variances between the current computer state and the data representative of the reference state; performing at least one remedial action when the verification program identifies the same or a different variance between the current computer state and the reference state; and launching the main operating system and stopping and unloading the pre-boot operating system when the verification program does not re-identify a variance between the current computer state and the reference state; and launching a main operating system and stopping and unloading the pre-boot operating system when no variance is identified (step 308). identifying a remedial data processing action to resolve an identified variance, the remedial data processing action being identified based on the identified variance; performing the remedial data processing action; re-identifying any variances between the current computer state and the data representative of the reference state; performing at least one remedial action when the verification program identifies the same or a different variance between the current computer state and the reference state; and launching the main operating system and stopping and unloading the pre-boot operating system when the verification program does not re-identify a variance between the current computer state and the reference state; and launching a main operating system and stopping and unloading the pre-boot operating system when no variance is identified (step 308).