Microsoft Certified Systems Engineer (MCSE) Question:

Trusted networks:
Such Networks allow data to be transferred transparently. The machines using a trusted network are usually administered by an Administrator to ensure that private and secured data is not leaked. Access to this network is limited. Computers using trusted networks are more secured and confidential because of strong firewalls.

Untrusted networks:
Such networks are usually administered by the owners. They can allow improper access to sensitive or personal data. These machines are usually separate. Such machines could me more prone to attacks.