A barrier is a construct intended to protect a target from a force or agent that could affect it in a manner that is not wanted. It may totally prevent the possibility of the unwanted effect, reduce the probability or potential magnitude of the effect, alter the nature of the effect, or initiate some kind of countermeasure. In any case, the purpose of the barrier is to protect the target. If the barrier is for some reason unable to provide this protection, or if the protection is weakened, the barrier is considered to be failed, ineffective, or insufficient.
Barriers can take many forms. Some of the more common forms include:
- physical (mechanical, electrical)
- administrative (signs, procedures)
- software-based (firewalls, virus scanners)
- mental (habits, inhibitions)
Some samples of barriers in the real world are:
- The shutdown and emergency systems of a nuclear reactor.
- Safety belts and airbags in an automobile.
- Passwords, access privileges, firewalls, and encryption in a network server.
- Personal equipment like hardhats, safety glasses, ear plugs, and safety shoes.
- Guard rails and warning signs around a natural or man-made hazard.
- Procedures, training, and supervisory oversight at an industrial facility.
Barriers are seldom perfect in isolation, which is why multiple barriers are often put in place to achieve the required level of protection. This is called defense-in-depth.
See all uses of the word barrier on this site.
by Bill Wilson