In a computer system operable at more than one privilege level, an interrupt security module handles interrupts without exposing a secret value of a register to virtual interrupt handling code that executes at a lower privilege level than the interrupt security module. The interrupt security module is configured to intercept interrupts generated while executing code at lower privilege levels. Upon receiving such an interrupt, the interrupt security module overwrites the secret value of the register with an unrelated constant. Subsequently, the interrupt security module generates a virtual interrupt corresponding to the interrupt and forwards the virtual interrupt to the virtual interrupt handling code. Advantageously, although the virtual interrupt handling code is able to determine the value of the register and consequently the unrelated constant, the virtual interrupt handling code is unable to determine the secret value.