It happens on two levels.
First, we analyze the threat based on the information that Transport Canada, or other law enforcement agencies provide us, because we are not an intelligence agency.
Then we assess the vulnerability of our physical facilities, which provides us with a risk assessment. We mitigate those risks through measures that may involve personnel, material resources, or technology. This strategic situation assessment is done almost annually.
It is also done tactically. Take an incident like the one in Fort Lauderdale, or in Brussels. We immediately conduct an assessment to find out whether the threat for us has changed. Does the way an incident took place somewhere else expose a vulnerability for us that perhaps we may not have seen? We study the response. We go and look. We have discussions with our colleagues in the other airport and law enforcement agencies to see how they reacted and how their response worked, so that we are improving ourselves on an ongoing basis.