It all began after buying a music CD at Amazon, to the writer's surprise after a while he realized his computer was infected with what Rootkit Hunters classified as hidden programs. Read the full article if you are interested in seeing how far Sony went with their DRM software.

Rootkits are cloaking technologies that hide files, Registry keys, and other system objects from diagnostic and security software, and they are usually employed by malware attempting to keep their implementation hidden.