Spyware programs are applications that gather information about users' Internet habits and movements. The data, when collected, is sent to the creators themselves or to third parties, either directly or after being stored on computer.
Spyware is installed on systems in numerous ways, including: Trojans installed without users' consent; web pages with certain ActiveX controls or code that exploit vulnerabilities; applications with shareware or freeware type licenses downloaded from the Internet, etc.
Spyware can be installed either with or without users' consent, and either with or without their knowledge about the data gathered and/or the use of it.
Vundo.C does not spread automatically using its own means. It needs an attacking user's intervention in order to reach the affected computer. The means of transmission used include, among others, floppy disks, CD-ROMs, email messages with attached files, Internet downloads, FTP, IRC channels, peer-to-peer (P2P) file sharing networks, etc.