The 
University of Arizona

Protection Tips

Because potential security risks can occur at a variety of levels, you need to set up security measures that provide multiple layers of defense against these risks. In general, when you connect to the Internet, you should not wonder if you will experience intrusion attempts or denial of service attacks. Instead, you should assume that you will experience a security problem. Consequently, your best defense is a thoughtful, proactive offense. Using a layered approach ensures that an attacker who penetrates one layer of defense will be stopped by a subsequent layer.