Security protocols are the small distributed programs which are omnipresent in our daily lives in areas such as online banking and commerce and mobile phones. Their purpose is to keep our transactions and personal data secure. Because these protocols are generally implemented on potentially insecure networks like the internet, they are notoriously difficult to devise. The field of symbolic analysis of security protocols has seen significant advances during the last few years. There is now a better understanding of decidability and complexity questions and successful automated tools for the pro.