Analyzing multiple logs for forensic evidence

Information stored in logs of a computer system is of crucial importance to gather forensic evidence of investigated actions or attacks. Analysis of this information should be rigorous and credible, hence it lends itself to formal methods. We propose a model checking approach to the formalization of the forensic analysis of logs. A set of logs is modeled as a tree whose labels are events extracted from the logs. In order to provide a structure to these events, we express each event as a term of algebra. The signature of the algebra is carefully chosen to include all relevant information necessary to conduct the analysis. Properties of the model, attack scenarios, and event sequences are expressed as formulas of a logic having dynamic, linear, temporal, and modal characteristics. Moreover, we provide a tableau-based proof system for this logic upon which a model checking algorithm can be developed. We use our model in a case study to demonstrate how events leading to an SYN attack can be reconstructed from a number of system logs.