The Brussels terror attacks have exposed the challenges of protecting so-called soft targets.
Soft targets are identified as everyday places where large crowds gather and where security is usually pretty minimal. These places can include shopping malls, hospitals, schools, stadiums, concert venues and vacation areas.
Security experts say it's about not letting terrorists change people's lives while keeping people safe.
Experts say keeping safe can't only be about increasing police presence. They say it also has to be about encouraging communities to become more involved in helping protect themselves.
"You have to engage everybody," says law enforcement expert Denis Monette. "I think some of the best people you can engage in the community (are) the UPS driver or the FedEx drivers, the cab drivers, the mailman."