Security level 1 means the level for which minimum appropriate protective security measures must be maintained at all times (i.e. normal security).
Security level 2 means the level for which appropriate additional protective security measures must be maintained for a period of time as a result of heightened risk of a security incident (i. e. heightened security). Security level 3 means the level for which further specific protective security measures must be maintained for a limited period of time when a security incident is probable or imminent, although it may not be possible to identify the specific target (i. e. exceptional security).
