Intrusion Detection System (IDS)
A computer intrusion is the number of events that breaches the
security of a system. Such number of events must be detected in
proactive manner in order to guarantee the confidentiality, integrity
and availability of resources of a computer system. An intrusion into an
information system is a malicious activity that compromises its
security (e.g. integrity, confidentiality, and availability) through a
series of events in the information system. For example intrusion may
compromise the integrity and confidentiality of an information system by
gaining root level access and then modifying and stealing information.
Another type of intrusion is denial-of-service intrusion that
compromises the availability of an information system by flooding a
server with an overwhelming number of service requests to the server
over short period of time and thus makes services unavailable to
legitimate users. According to D. Yang, A. Usynin & W. Hines, they
describe intrusion and intrusion detection as: "Any action that is not
legally allowed for a user to take towards an information system is
called intrusion and intrusion detection is a process of detecting and
tracing inappropriate, and incorrect, or anomalous activity targeted at
computing and networking resources".