In-vehicle security systems, anti-theft causes the horn to sound and the lights to flash if someone tries to break into your vehicle. There are several different ways to trigger the alarm.

• Typically, the driver sets the alarm by operating a switch when leaving the car. Opening or forcing the hood, trunk, tailgate, or door to open also causes the alarm to trigger.
• Many vehicle security systems include a starter interruption, which prevents starting the engine after any forced entry. Some vehicles automatically disconnect electrical circuits to stop a car from starting or shut down the engine. 

Some examples of anti-theft security systems equipped on vehicles are brake lock, GPS tracker, hidden kill switch, steering wheel lock, battery disconnect switch, and an audible alarm.