a. you), a topic discussed in detail in the next
section. One particular type of virus, a Trojan horse, spreads itself by masquerading
as a benign application (as opposed to infecting an otherwise
valid file), such as a screensaver or even, ironically, a virus removal tool.
Worms
A worm* is a special type of virus that can infect a computer without any
help from its user, typically through a network or Internet connection.
Worms can replicate themselves like ordinary viruses, but do not
spread by infecting programs or documents. A classic example is the
W32.Blaster.Worm, which exploited a bug in Windows XP, causing it
to restart repeatedly or simply seize up.
Spyware and adware
Spyware is a little different than the aforementioned viruses and worms,
in that its purpose is not necessarily to hobble a computer or destroy
data, but rather something much more insidious. Spyware is designed to
install itself transparently on your system, spy on you, and then send the
data it collects back to an Internet server. This is sometimes done to collect
information about unsuspecting users, but most often to serve as a
conduit for pop-up advertisements (known as adware).
* The term worm is said to have its roots in J.R.R. Tolkien, who described dragons in Middle Earth
that were powerful enough to lay waste to entire regions. Two such dragons (Scatha and Glaurung)
were known as ???the Great Worms.??? The Great Worm, a virus written by Robert T.
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