A security alarm is a system designed to detect intrusion, such as unauthorized entry, into a building or other areas such as a home or school. Security alarms protect against burglary (theft) or property damage, as well as against intruders. Examples include personal systems, security alerts in neighborhoods, car alarms, and prisons.

A security system safeguards a home or building from intruders by securing entry points, like doors and windows (including basement windows), as well as its interior space. In most cases, outside forces will trip a home security system’s alarm and alert law enforcement or homeowners so that they can interfere.