What is an audit in an information system and why is it needed?

An audit in an information system is a process of systematically checking and analyzing actions, operations, and events within the system to ensure security, compliance with policies and standards, as well as to identify and prevent violations. It is necessary for access control, tracking changes, detecting security incidents, and confirming the correct operation of the system. For example, an audit allows understanding who and when changed important data, which helps in incident investigation and increasing trust in the system.