中文摘要：

信息系统中的资源是海量的，而且这些资源的状态又是不断变化的，这都大大增加了进行危险感知的难度，常规的方法难以应对．一切异常必然在系统的某些外在属性上留下痕迹，并带来系统资源的变化．变化及变化趋势是安全异常检测的基础．通过研究变化及变化趋势，来从新的角度研究危险感知．借鉴了数学中微分的概念，提出运用数字微分的方法来描述系统中信息资源的变化及变化趋势，并指出数字微分的奇异点就是危险，通过对变化及变化趋势的检测来感知系统的危险，从而产生危险信号．

英文摘要：

The resource of information system is huge and its state is changing all the time. The difficulty to sense danger increased due to this can＇t be dealt with common method. Traces will be left on the system＇s exterior attributes and the system resource will be changed by any abnormalities. The change and its trend are the basis of abnormal detection. The danger can be sensed from different aspects. Differential calculus in math is used for reference and numerical differential method is presented to describe change and its trend of the system resource. Danger can be indicated by the abnormal point of numerical differential. System＇s threat is sensed through change and its trend detection and then dangerous signal is generated.