There are two main variations: Inbound: the product contains an authentication mechanism that checks the input credentials against a hard-coded set of credentials. In this variant, a default administration account is created, and a simple password is hard-coded into the product and associated with that account. This hard-coded password is the same for each installation of the product, and it usually cannot be changed or disabled by system administrators without manually modifying the program, or otherwise patching the product.

It can also be difficult for the administrator to detect. Outbound: the product connects to another system or component, and it contains hard-coded credentials for connecting to that component. This variant applies to front-end systems that authenticate with a back-end service.

The back-end service may require a fixed password that can be easily discovered. The programmer may simply hard-code those back-end credentials into the front-end product.