Security is for avoiding dangers or losses. In general, security is similar to safety. The difference between the two is security cares more about dangers from the outside than general safety.
Airports and banks usually have a lot of security measures. Prison security is mainly to stop prisoners from escaping. It is also to stop prisoners from harming prison employeesor other prisoners.
Maximum security is in or around prisons or other types of places where people need to be kept in or kept out. It is the highest security level for a building or area.