spyware

Any software that covertly gathers user information through
the user's Internet connection without his or her knowledge,
usually for advertising purposes. Spyware applications are typically
bundled as a hidden component of freeware or shareware programs
that can be downloaded from the Internet; however, it should be
noted that the majority of shareware and freeware applications
do not come with spyware. Once installed, the spyware monitors
user activity on the Internet and transmits that information
in the background to someone else. Spyware can also gather
information about e-mail addresses and even passwords and
credit card numbers.

Spyware is similar to a Trojan horse in that users unwittingly
install the product when they install something else.
A common way to become a victim of spyware is to download
certain peer-to-peer file swapping products that are available today.

Aside from the questions of ethics and privacy, spyware steals
from the user by using the computer's memory resources and also
by eating bandwidth as it sends information back to
the spyware's home base via the user's Internet connection.
Because spyware is using memory and system resources,
the applications running in the background can lead to
system crashes or general system instability.

Because spyware exists as independent executable programs,
they have the ability to monitor keystrokes, scan files on
the hard drive, snoop other applications, such as chat programs
or word processors, install other spyware programs, read cookies,
change the default home page on the Web browser, consistently
relaying this information back to the spyware author who will
either use it for advertising/marketing purposes or sell
the information to another party.

Licensing agreements that accompany software downloads sometimes
warn the user that a spyware program will be installed along with
the requested software, but the licensing agreements may not
always be read completely because the notice of a spyware
installation is often couched in obtuse,
hard-to-read legal disclaimers.