Information technology (IT) is essential to virtually all critical infrastructures, making them vulnerable to a terrorist attack. An attack could be on the system itself or use the IT system to launch or exacerbate another type of attack. IT can also be used as a counterterrorism tool. This report states that the most devastating consequences of a terrorist attack would occur if it were on or used IT as part of a broader attack. It presents two recommendations on what can be done in the short term to protect communications and information systems and several recommendations about what can be done over the longer term. The report also notes the importance of considering how an IT system will be deployed to maximize protection against and usefulness in responding to attacks.