A dialer is a program that installs itself on your computer and will dial a long distance number using your modem to connect you to various types of content. Often, the content dialers connect you to are pornography related. Many people who have inadvertently installed dialers on there computers, have ended up with some extremely high phone bills. The best way to prevent the installation of these pests is to never download anything unless you know what it is. Dialer downloads are often prompted in pop-ups and some sites require a dialer to be installed to access content. Using a pop-up blocker is also a recommended tool to prevent the installation of dialers.