Preventive controls are security measures that are put in place to prevent incidents from happening. They are proactive in nature and aim to stop threats before they can cause harm. Examples of preventive controls include firewalls, which block unauthorized access, and access controls, which restrict access to sensitive resources. Detective controls, on the other hand, are designed to identify and respond to incidents after they have occurred. Corrective controls aim to limit the damage after an incident, while compensating controls substitute for primary controls.