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Malicious Code Guide
by Enrique De
This article is dedicated as a
guide to provide you with information on the different types of
malicious code that can affect the performance of your computer.
It will be extended as more content becomes available.
Adware is advertising-supported
software that displays pop-up advertisements whenever the program
is running. The software is usually available via free download
from the Internet, and it is the advertisements that create
revenue for the company. Although seemingly harmless (aside from
intrusiveness and annoyance of pop-up ads), adware can install
components onto your computer that track personal information
(including your age, gender, location, buying preferences,
surfing habits, etc.).
Most advertising supported
software doesn't inform you that it installs adware on your
system, other than via buried reference in a license agreement.
In many cases the software will not function without the adware
component. Some Adware can install itself on your computer even
if you decline the offer.
System monitors are
applications designed to monitor computer activity to various
degrees. These programs can capture virtually everything you do
on your computer including recording all keystrokes, emails, chat
room dialogue, web sites visited, and programs run. System
monitors usually run in the background so that you do not know
that you are being monitored. The information gathered by the
system monitor is stored on your computer in an encrypted log
file for later retrieval.
Some programs are capable of
emailing the log files to another location. Traditionally, system
monitors had to be installed by someone with administrative
access to your computer, such as a system administrator or
someone that shares your computer. However, there has been a
recent wave of system monitoring tools disguised as email
attachments or "freeware" software products.
They usually carry out
their actions without the user noticing. Trojans Horses or
Trojans are malicious programs that appear as harmless or
desirable applications. Trojans are designed to cause loss or
theft of computer data, and to destroy your system. Some Trojans,
called RATs (Remote Administration Tools), allow an attacker to
gain unrestricted access of your computer whenever you are
online. The attacker can perform activities such as file
transfers, adding/deleting files or programs, and controlling the
mouse and keyboard. Trojans are generally distributed as email
attachments or bundled with another software program.
Trojans are named after the
mythical Horse of Troy, a large, wooden horse that Greek soldiers
left at the doors of the city of Troy, after a long battle.
Thinking that the Greek army had withdrawn, the Trojans took the
horse into the city. However, at nightfall, the Greeks got out of
the horse and attacked the city, thus destroying the city of
In computing, Trojans are, apparently harmless programs that
after reaching a computer, carry out several actions without the
user noticing. Unlike other malicious code, Trojans do not
replicate by infecting other computers and so their capacity to
spread is limited.
Depending on the actions they carry out on the affected
computers, Trojans can be classified into the following
- Destructive Trojans are designed to delete certain files,
format the hard disk, or carry out similar destructive
- Backdoor Trojans are designed open a backdoor in the computer
to let hackers enter and take remote control of it. For this
reason they consist of two components: the server, installed on
the machine under attack and the client, used by the hacker to
control the computer.
- Keylogger Trojans are programmed to capture the user's
keystrokes. This information is stored in a special log that can
be accessed by the attacker.
- Fake Trojans, which after being run, display false error
messages prompting users to enter user names and passwords which
are then sent on to the creator of the malicious code.
For further information on Trojans or other type of malicious
code, visit the following websites:
There are many other suspicious
and/or annoying programs that can find their way onto your
computer without your express knowledge. These programs often
come bundled with third-party programs or can be installed as
“drive-by downloads.” Some of these programs have
spyware capabilities, while others may serve as an annoyance or
negatively affect your system resources. There are many terms for
these types of programs including scumware, annoyanceware,
parasites, malware, etc.
For safe security software, visit the Software Gallery.
About the Author:
Enrique de Argaez is the webmaster of several
multilingual Internet websites and author of four newsletters. He
is active in Internet World Marketing, and Internet Market
Research. Visit his main English website at http://www.internetworldstats.com