back door

definition: a secret or underhand means of access to a place or a position
example: I got my job through the back door.
speech part: noun
synonyms: backdoor
definition: an entrance at the rear of a building
example:
speech part: noun
synonyms: backdoor back entrance
definition: an undocumented way to get access to a computer system or the data it contains
example:
speech part: noun
synonyms: backdoor

How back door is being used?