Detection of anomalous computer session activity

The authors discusses Wisdom and Sense (W&S), a computer security anomaly detection system. W&S is statistically based. It automatically generates rules from historical data and, in terms of those rules, identifies computer transactions that are at variance with historically established usage patterns. Issues addressed include how W&S generates rules from a necessarily small sample of all possible transactions, how W&S deals with inherently categorical data, and how W&S assists system security officers in their review of audit logs. Preliminary results with W&S show that the software does periodically detect anomalies of high interest even in data though to be free of such events.>