Computer security is a rapidly changing subject. Administrators and information security professionals invent and adopt a variety of terms and phrases to describe potential risks or uninvited incidents to computers and networks. The following is a list of these terms and their meanings as used in this document.

Some of these terms refer to real security risks and some refer to annoying or unsolicited incidents. Trojans, viruses/malware, and worms are examples of terms used to describe real security risks. Joke programs, spyware/grayware are terms used to describe incidents that might be harmful, but are sometimes simply annoying and unsolicited. ScanMail can protect Exchange servers against all of the incidents described in this chapter.