A technician needs to disable guest log-ins on domain-joined desktop machines.

Disabling guest accounts on domain-joined machines is done through Group Policy. Group Policy allows centralized management and configuration of operating systems, applications, and users' settings in an Active Directory environment. By using the Group Policy Editor (gpedit.msc), administrators can enforce policies such as disabling the guest account across all machines within the domain. The other options (Firewall, Microsoft Management Console, MSConfig) do not provide functionality specific to managing user accounts in this context.