Spyware is a type of malware (malicious software) installed on
computers that collects information about users without their
knowledge. The presence of spyware is typically hidden from the
user and can be difficult to detect. Spyware is often secretly
installed on a user's personal computer without their knowledge.
However, some spyware such as keyloggers may be installed by the
owner of a shared, corporate, or public computer on purpose in
order to intentionally monitor users.
While the term spyware suggests software that monitors a user's
computing, the functions of spyware can extend beyond simple
monitoring. Spyware can collect almost any type of data, including
personal information like Internet surfing habits, user logins, and
bank or credit account information. Spyware can also interfere with
user control of a computer by installing additional software or
redirecting Web browsers. Some spyware can change computer
settings, resulting in slow Internet connection speeds,
un-authorized changes in browser settings or functionality of other
software.
Sometimes, spyware is included along with genuine software, and
may come from an official software vendor. In an attempt to
increase the understanding of spyware, a more formal classification
of its included software types is provided by the term
privacy-invasive software. In response to the emergence of spyware,
a small industry has sprung up dealing in anti-spyware software.
Running anti-spyware software has become a widely recognized
element of computer security practices for computers, especially
those running Microsoft Windows. A number of jurisdictions have
passed anti-spyware laws, which usually target any software that is
surreptitiously installed to control a user's computer. A computer
virus is a computer program that can replicate itself[1] and spread
from one computer to another. The term "virus" is also commonly,
but erroneously, used to refer to other types of malware, including
but not limited to adware and spyware programs that do not have a
reproductive ability.