Directed infrared countermeasures (DIRCM) play an increasingly important role in electronic warfare to counteract threats posed by infrared seekers. The usefulness and performance of such countermeasures depend for example on atmospheric conditions and platform vibrations, causing pointing and tracking errors for the laser beam and reducing the power transferred to the seeker aperture. This report describes a computer model of such a system that has been developed and implemented as a part of a large real-time simulation framework, EWSim. The framework also incorporates several seekers and models of robot dynamics. Effects of a jamming laser on a specific threat can be readily verified by simulations within this framework. The report covers the whole chain from modelling to simulation and verification. Simulations of tracking and jamming are included, all of which producing plausible results. The jamming simulations were compared to experimental data in an attempt to verify the models. For the special case that was tested, the model could be adjusted by its parameters to agree well with the experiments. Thus it is likely that the model can produce realistic results in similar cases.