trigger Symantec Sygate Enterprise Protection only. An event that causes a firewall rule to take effect. When creating rules, you can assign specific triggers, which cause Protection Agents to react in a specific way, and actions, which specify what to do when the trigger takes place. For example, you can block all traffic originating from a certain IP address or block traffic during certain hours of the day. Triggers can be linked to specific applications, hosts, schedules, and services.