Cyber security operators in the military and civilian sector face a lengthy repetitive work assignment with few critical signal occurrences under conditions in which they have little control over what transpires. In this sense, their task is similar to vigilance tasks that have received considerable attention from human factors specialists in regard to other operational assignments such as air traffic control, industrial process control, and medical monitoring. Accordingly, this study was designed to determine if cyber security tasks can be linked to more traditional vigilance tasks in regard to several factors known to influence vigilance performance and perceived mental workload including time on task, the probability of critical signal occurrence, and event rate (the number of stimulus events that must be monitored in order to detect critical signals). Consistent with the results obtained in traditional vigilance experiments, signal detection on a 40- minute simulated cyber security task declined significantly over time, was directly related to signal probability, and inversely related to event rate. In addition, as in traditional vigilance tasks, perceived mental workload in the cyber task, as reflected by the NASA Task Load Index, was high. The results of this study have potential meaning for designers of cyber security systems in regard to psychophysical factors that might influence task performance and the need to keep the workload of such systems from exceeding the information processing bounds of security operators.