Your homepage is your home. Toolbars are one of the most common and annoying potentially unwanted programs. Toolbars change your homepage and search settings, often without your consent. If your homepage is not easily recognized (Yahoo.com, Google.com, or Bing.com), you may have a toolbar installed.
DNS is your internet "speed dial". DNS is the system and protocol that allows you to connect to a website through its domain name instead of its IP address. Some potentially unwanted programs change your DNS settings or otherwise intercept your DNS in order to generate ad revenue, or in some cases, to steal your personal data or information. When you have a DNS redirector installed, it may be difficult to tell if you are sending your online banking username and password to your bank, or to a malicious third party.
SSL is your secure channel to the internet. SSL interceptors are tricky; they often operate as a local system proxy or packet inspector, silently observing everything that you do on the internet. They are capable of injecting ads into your web experience, as well as stealing usernames, passwords, email addresses, and other important personal information. Because SSL interceptors operate as a man-in-the-middle, they have complete access to virtually all of your online activity and data.
Your browsing experience should be clutter-free. Ad injectors are a broad category of potentially unwanted programs which alter the content of sites you visit in one way or another. Generally, ad injectors are responsible for pop-ups and another annoying advertisements which you may not otherwise commonly see. Many ad injectors operate as browser extensions, sometimes out of the purview of traditional anti-virus software. If you've noticed an increase in pop-ups or other forms of advertisement on your favorite sites, you may have an ad injector installed.