We face many challenges when designing, developing, using, and supporting the computers and software collectively called the "cyber infrastructure." This vast system is the backbone on which more and more of our commerce and communication are based, so we protect it by plugging the cyber security "holes" caused by built-in vulnerabilities. In doing so, we deal with unwelcome outages and changes, the consequences of which can range from temporary annoyance to long-term destruction of property or way of life.