Computer Virus: Way they infects

After reading this post you will get to know virus type and how they work,

I have describe them in short.

Adware is software that presents banner ads or in pop-up windows through a
bar that appears on a computer screen. Those advertising spots usually can’t be
removed and are consequently always visible. The connection data allow many
conclusions on the usage behavior and are problematic in terms of data
A backdoor can gain access to a computer by going around the computer access
security mechanisms.
A program that is being executed in the background generally enables the
attacker almost unlimited rights. User’s personal data can be spied with the
backdoor’s help, but are mainly used to install further computer viruses or
worms on the relevant system.

Boot viruses
The boot or master boot sector of hard drives is mainly infected by boot sector
viruses. They overwrite important information necessary for the system
execution. One of the awkward consequences, the computer system cannot be
loaded any more…
A Bot-Net is collection of softwarre bots, which run autonomously. A Bot-Net
can comprise a collection of cracked machines running programs (usually
referred to as worms, Trojans) under a common command and control
infrastructure. Boot-Nets server various purposes, including Denial-of-service
attacks, etc., partly without the affected PC user’s knowledge. The main
potential of Bot-Nets is that the networks can achieve dimensions on thousands
of computers and its bandwidth sum bursts most conventional Internet
A dialer is a computer programm that establishes a connection to the Internet
or to another computer network through the telephone line or the digital ISDN
network. Fraudsters use dialers to charge users high rates when dialing up to
the Internet without their knowledge.
EICAR test file
The EICAR test file is a test pattern that was developed at the European
Institute for Computer Antivirus Research for the purpose to test the functions
of anti-virus programs. It is a text file which is 68 characters long and its file
extension is “.COM” all virus scanners should recognize as virus.
An exploit (security gap) is a computer program or script that takes advantage
of a bug, glitch or vulnerability leading to privilege escalation or denial of
service on a computer system. A form of an exploit for example are attacks
from the Internet with the help of manipulated data packages. Programs can
be infiltrated in order to obtain higher access.

Grayware operates in a way similar to malware, but it is not spread to harm
the users directly. It does not affect the system functionality as such. Mostly,
information on the patterns of use is collected in order to either sell these data
or to place advertisements systematically.

The users have obtained virus alerts from the Internet for a few years and
alerts against viruses in other networks that are supposed to spread via email.
These alerts are spread per email with the request that they should be sent to
the highest possible number of colleagues and to other users, in order to warn
everyone against the “danger”.
A honeypot is a service (program or server), which is installed in a network.
It has the function to monitor a network and to protocol attacks. This service is
unknown to the legitime user – because of this reason he is never addressed. If
an attacker examines a network for the weak points and uses the services
which are offered by a Honeypot, it is protocolled and an alert sets off.
Keystroke logging
Keystroke logging is a diagnostic tool used in software development that
captures the user’s keystrokes. It can be useful to determine sources of error in
computer systems and is sometimes used to measure employee productivity on
certain clerical tasks. Like this, confidential and personal data, such as
passwords or PINs, can be spied and sent to other computers via the Internet.
Macro viruses
Macro viruses are small programs that are written in the macro language of an
application (e.g. WordBasic under WinWord 6.0) and that can normally only
spread within documents of this application. Because of this, they are also
called document viruses. In order to be active, they need that the
corresponding applications are activated and that one of the infected macros
has been executed. Unlike “normal” viruses, macro viruses do consequently not
attack executable files but they do attack the documents of the corresponding
Malware is short name from “Mallicious-ware”. Unknown virus is detected as
Malware. Malware using script or codes to execute itself (autorun.inf).
Infection is same like script virus/worms. Once execute, it will proceed to
system files windows and modify important system setting (Like disabling the
Task Manager, Folder Option and Registry Editing). This will make the computer
more risk in security measures.
Polymorph viruses
Polymorph viruses are the real masters of disguise. They change their own
programming codes – and are therefore very hard to detect.
Program viruses
A computer virus is a program that is capable to attach itself to other programs
after being executed and cause an infection. Viruses multiply themselves unlike
logic bombs and Trojans. In contrast to a worm, a virus always requires a
program as host, where the virus deposits his virulent code. The program
execution of the host itself is not changed as a rule.

Script viruses and worms
Such viruses are extremely easy to program and they can spread – if the
required technology is on hand – within a few hours via email round the globe.
Script viruses and worms use a script language such as Javascript, VBScript etc.
to infiltrate in other new scripts or to spread by activation of operating system
functions. This frequently happens via email or through the exchange of files
A worm is a program that multiplies itself but that does not infect the host.
Worms can consequently not form part of other program sequences. Worms are
often the only possibility to infiltrate any kind of damaging programs on
systems with restrictive security measures.

Spyware are so called spy programs that intercept or take partial control of a
computer’s operation without the user’s informed consent. Spyware is designed
to expolit infected computers for commerical gain. Typical tactics furthering
this goal include delivery of unsolicited pop-up advertisements. AntiVir is able
to detect this kind of software with the category “ADSPY” or “adware-spyware”.

Trojan horses (short Trojans)
Trojans are pretty common nowadays. We are talking about programs that
pretend to have a particular function, but that show their real image after
execution and carry out a different function that, in most cases, is destructive.
Trojan horses cannot multiply themselves, which differenciates them from
viruses and worms. Most of them have an interesting name (SEX.EXE or
STARTME.EXE) with the intention to induce the user to start the Trojan.
Immediately after execution they become active and can, for example, format
the hard drive. A dropper is a special form of Trojan that ‘drops’ viruses, i.e.
embeds viruses on the computer system. (Usually some trojans come with help
of ” autorun.inf ” files to execute automatically from diskette or portable
device to infect other computer).
A Zombie-PC is a computer that is infected with malware programs and that
enables hackers to abuse computers via remote control for criminal purposes.
The affected PC, for example, can start Denial-of-Service- (DoS) attacks at
command or send spam and phishing emails.


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