If an intrusion is required to be an intruder, then it seems that all intruders are attackers, but all attackers are not necessarily intruders. The concept of an unsuccessful intrusion is not common in colloquial English, but it is common in information assurance. This causes ambiguity in use in information assurance. Some uses seem to encompass both successful and unsuccessful intrusions, while others seem to imply successful intrusions only and unsuccessful intrusions are just attacks. It is unclear whether an unsuccessful attack is an intrusion.
Intrusion seems to imply forced entry, while attack seems to only imply the application of force.
A combination of hardware and software that monitors and collects system and network information and analyzes it to determine if an attack or an intrusion has occurred. Some ID systems can automatically respond to an intrusion. Used together, ID technologies can provide accurate indicators of whether or not an attack or intrusion has occurred. Missions are not limited to military settings since any successful organization or project must have a vision of its objectives whether expressed implicitly or as a formal mission statement. Judgments as to whether or not a mission has been successfully fulfilled are typically made in the context of external conditions that may affect the achievement of that mission.