An interrupt descriptor table (IDT) is used by a processor to transfer the execution of a program to software routines that handle interrupts raised during the normal course of operation or to signal an exceptional condition such as a hardware failure. Attackers frequently modify IDT pointers to execute malicious code. This paper describes the IDTchecker tool, which uses a rule-based approach to check the integrity of the IDT and the corresponding interrupt handling code based on a common scenario encountered in cloud environments. In this scenario, multiple virtual machines (VMs) run the same version of an operating system kernel, which implies that IDT-related code should also be identical across the pool of VMs. IDTchecker leverages this scenario to compare the IDTs and the corresponding interrupt handlers across the VMs for inconsistencies based on a pre-defined set of rules. Experimental results related to the effectiveness and runtime performance of IDTchecker are presented. The results demonstrate that IDTchecker can detect IDT and interrupt handling code modifications without much impact on guest VM resources.