Configuration Drift describes the result of Entropy acting on a set of servers within the same group, continuously furthering differences in their configuration as time goes on.
This phenomenon affects any computer systems / server fleets that have a manual configuration component and are not fully made up of Immutable Infrastructure.
To eliminate the drift, server configuration and setup must be fully moved to OS Configuration Management and Infrastructure as Code maintenance.
However, even in fully automated infrastructures Configuration Drift can be introduced, for example as a result of critical patches / fixes during incidents or alike.
Configuration Drift adds to the Technical Debt of an infrastructure.