Internet cycle sharing systems that utilize idle computing resources dramatically increase the available resources for high performance computing. Fraudulent resource providers, however, can subvert these systems. While previous research has investigated protection against resource providers that return bad results, we consider a different fraudulent behavior cycle short-changing in which the resource provider faithfully executes the submitted job, but using a smaller percentage of the CPU resources than he/she promises. To detect this short-changing, we propose CycleMeter, a tool that allows a remotely executing application to accurately monitor the percentage of CPU resources it is utilizing throughout its execution period. CycleMeter employs a microbenchmark to measure the instantaneous CPU utilization of the application, and employs a simple and practical mechanism for embedding the microbenchmark into the application. Our experimental results on three operating systems and uniprocessor and multiprocessor machines show that CycleMeter is portable, incurs a low overhead, and is highly effective in detecting a spectrum of cycle shortchanging behavior.