Virus: A program that copies itself into another
program, sectors on a drive, or items that support
scripts. Most viruses only copy themselves, while a
minority unleash a payload, which is the action
generated by the virus. Payloads can damage files,
corrupt hard drives, display messages, or open other
files. Typically, the payload is delivered when a
certain condition occurs, such as when the date on
the computer reaches a particular day.
Virus variant: A virus that has been altered to
take advantage of already created virus code. By
doing this, the virus is not immediately detected by
antivirus software looking for the original virus.
Worm: A more effective form of virus that finds
vulnerable systems and then copies itself into those
systems. The most frequent methods of propagation
are from email distribution lists, email signature
scripts, and shared folders on the network. Worms
may or may not have a damaging payload. Currently
the typical payload for a worm is making the
computer more susceptible to other malicious
viruses.
Superworm: A worm that sends itself out to other
vulnerable systems only after it has detected many
systems and made a "list." All infected computers
send at roughly the same time. This makes virus
detection more difficult and greatly increases the
number of computers it can infect in less time.
Hoax: An email that usually states that it is
harming the computer, but does not actually perform
what it states. Some hoaxes ask the reader of the
email to perform a damaging process, like deleting
an important file. Most hoaxes are spread by
well-meaning individuals hoping to alert others to a
potential virus that in reality is just a hoax.
Trojan or Trojan Horse: A Trojan or Trojan Horse
is a program generally designed to impact the
security of a system. The program is usually
disguised as something else (a benign program) or is
masqueraded as a legitimate file that the user would
expect to see, or want to load, on the system. The
payload of a Trojan is usually delivered as soon as
it is opened and usually with devastating results.
Backdoor Trojan:
A backdoor trojan differs from a trojan in that it
also opens a backdoor to your system. They’re also
sometimes call Remote Access Trojans (RAT). These
are the most widespread and also the most dangerous
type of trojan. They are so dangerous because the
have the potential to allow remote administration of
your system. As if a hacker were sitting at your
keyboard, only worse. There’s almost no limit to
what they can do. Some common uses:
Use your system
and Internet connection to send spam.
(yes, the
majority of spam is now generated by infected
systems).
Steal your
online and offline passwords, credit card
numbers, address, phone number, and other
information stored on your computer that could
be used for identity theft, or other financial
fraud.
Log your
activity, read email, view and download contents
of documents, pictures, videos and other private
data.
Use your
computer and Internet connection, in conjunction
with others to launch Distributed Denial of
Service (DDoS) attacks. Modify system files,
disable antivirus, delete files, change system
settings, to cover tracks, or just to wreak
havoc.
Phishing: phishers lure users to a phony web site,
usually by sending them an authentic-appearing
email. Once at the fake site, users are tricked into
divulging a variety of private information, such as
passwords and account numbers.
Pharming: pharming allows hackers to
redirect one website's traffic to another
website. At the bogus site, the pharmer uses
his old phishing tricks to obtain sensitive
data and IDs from users. Pharming is a
particularly virulent threat.
Spyware: spyware invades a computer then,
as its name implies, monitors a user's
activities without consent. Despite much
press over the past year, spyware continues
to infect millions of computers every year.
Insidious and devious, spyware can be
difficult to purge even when detected.
Zombie drones: zombie drones allow
hackers to turn third-party computers into
remote spamming machines. As a result, a
user may play an unwitting role in
propagating spam.
Keep your
precious data 
