Intrusions

Intrusions refer to acts of entering a space or domain without permission, as well as to geologic formations formed when magma forces its way into surrounding rock and cools underground.

Geologic intrusions form when magma forces its way into surrounding rock and cools underground. They can take several forms: dikes, which cut across existing rock; sills, which lie parallel to layering; and larger bodies called plutons. When substantial, plutons may surface as batholiths. The intrusion heats and may metamorphose adjacent rock, producing contact metamorphism and mineral changes. Because they crystallize below the surface, they differ from lava flows, which erupt onto the ground.

In information security, an intrusion is unauthorized access to a computer system or network. Intrusions may be conducted by criminals, insiders, or state actors and can be targeted or opportunistic. Detection relies on defense in depth, including access controls, auditing, and intrusion detection systems that monitor traffic and logs. Common techniques include phishing, credential theft, malware, exploitation of unpatched software, and social engineering. Responses emphasize containment, forensics, and remediation, such as patching vulnerabilities, revoking credentials, and strengthening monitoring to prevent recurrence.

Other uses include intrusion into personal space or property, or incursions by military forces into territory.