Last year, anonymous executives at Sony BMG Music Entertainment blundered. They hid a "rootkit" on around two million compact discs.

As senior editor Wade Roush explains in this month's cover story, "Inside the Spyware Scandal," rootkits are a kind of software more often exploited by mischievous hackers than by multinational media companies: a rootkit is capable of exposing an operating system's core functions to worms, viruses, or other programs, without anyone knowing about the subterfuge. In this case, computer users were asked to launch a Sony music player when they tried to play a Sony CD; if they did, they unwittingly downloaded a rootkit intended to hide components of a digital rights management (DRM) program. The DRM program also secretly contacted Sony every time a user played copy-protected music.

Sony's executives thought they were within their rights: they wanted to discourage piracy. But when security experts discovered the rootkit and blogged about it, a scandal followed. Many computer users said they felt "violated." According to John Guarino, the computer consultant who first identified the rootkit, "It's total lawlessness, and it's unacceptable."