An Introduction to Intrusion-Detection Systems

Intrusion-detection systems aim at detecting attacks against computer systems and networks or, in general, against information systems. Indeed, it is difficult to provide provably secure information systems and to maintain them in such a secure state during their lifetime and utilization. Sometimes, legacy or operational constraints do not even allow the definition of a fully secure information system. Therefore, intrusion–detection systems have the task of monitoring the usage of such systems to detect any apparition of insecure states. They detect attempts and active misuse either by legitimate users of the information systems or by external parties to abuse their privileges or exploit security vulnerabilities. This paper is the first in a two-part series; it introduces the concepts used in intrusion–detection systems around a taxonomy.