Tom installs a Telnet application on his Windows Vista system. When he first starts the program, Windows Firewall pops up with a message telling him the Telenet application is trying to access the Internet. If he clicks on the Allow button, what has he created?

Exception

Explanation:

Based on the scenario being described within the question it can be said that by clicking the allow button he is creating an exception in the windows firewall. This refers to letting the firewall know that the telnet application is safe and can be allowed to bypass the firewall without being stopped. Therefore making it an exception on the firewalls list of potential hazards.