A firewall controls all the traffic coming in to or going out from your site to the Internet. A firewall puts an electronic security guard at your place of business to enforce rules for who can gain admittance to what resources, and for what purpose. Those rules are enforced in both directions, so your employees also have controls placed on what they can do and how much information leaves your site. All entry in to or out from your network can be logged, including anything that violated a rule and was unsuccessful.