... usage.¹

Deciding whether a particular program should be called spyware or not can be both difficult and delicate. In practice, there is a continuous spectrum of program behavior that spans from malicious and invasive to fully legitimate. In this paper, we use the term spyware very broadly, and in general apply the term as might be commensurate with the experience of an unsophisticated user. However, we are careful to describe the precise behavior of individual programs discussed in this paper.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

... spyware.²

Kazaa is now distributed in two versions: a free version that contains spyware, and a paid version without spyware.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

... programs.³

Note that we could not measure spyware installations on computers that were inactive during our tracing period, so this number is conservative.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.