Drive-by download URLs are URLs that promote the unintended download of software from websites. They could be downloaded when a naive user first clicks on a URL, without knowing the consequences of this action. Drive-by downloads could also result from downloads that are carried out by malware that has infected a system. Drive-by downloads are the most prevalent form of attack.
The following diagram shows a drive-by download, and explains how a malicious email is first sent to the user and gets downloaded to the user's computer:
