Systems put in place to keep people from getting access to resources they shouldn't have access to.

Tracking whether or not the systems have been accessed

Preventative: limits access to the resource

Deterrent: disincentivizing people from accessing a resource through consequences, threats, warnings, etc

Detective: keeping track of who has accessed what so you can determine if someone has accessed a resource. Such as logs, video cameras.

Corrective: fixing the issue, or invoking consequences such as contacting authorities or rolling back the corrupted data.

Access badge - secures inside building

Access control vestibule - in building lobby, kind of like an air gap between places with two doors. also known as a man trap

power generator - physical, availability, corrective