Group Policy is the Microsoft Active Directory mechanism for centrally enforcing system and security configurations on Windows devices. Group Policies consist of individual Group Policy Objects (GPOs) applied hierarchically to sites, domains, and organizational units.
Group Policy controls hundreds of settings: from password complexity through firewall configuration to restricting executable software. The order of application (LSDOU: Local, Site, Domain, OU) determines which policy wins in case of conflicts. For information security, Group Policy is the primary tool for hardening Windows environments. The ISMS should document which GPOs implement which security requirements and who is responsible for their maintenance.