|
|
|
The original
virus
may modify the copies, or the copies may
modify themselves, as occurs in a
metamorphic virus.
a virus can only spread from
one computer to another when its host is
taken to the uninfected computer, for
instance by a user sending it over a network
or the Internet, or by carrying it on a
removable medium such as a floppy disk, CD,
or
USb drive. Meanwhile
viruses can spread
to other computers by infecting files on a
network file system or a file system that is
accessed by another
computer.
Viruses are sometimes
confused with
computer worms
and
Trojan
horses. A worm can spread itself to
other computers without needing to be
transferred as part of a host, and a
Trojan
horse is a file that appears harmless. |
|
|
Worms and
Trojans may cause
harm to either a computer system's hosted
data, functional performance, or networking
throughput, when executed. In general, a
worm does not actually harm either the
system's hardware or
software, while at least in
theory, a
Trojan's payload may be capable of
almost any type of harm if executed.
Some can't be seen when the
program is not running, but as soon as the
infected code is run, the
Trojan horse kicks
in. That is why it is so hard for people to
find
viruses and other malware themselves
and why they have to use
spyware programs
and
registry processors.
Most personal computers are
now connected to the
Internet and to local
area networks, facilitating the spread of
malicious code. Today's viruses may also
take advantage of network services such as
the World Wide Web,
e-mail, Instant
Messaging and
file sharing systems to
spread, blurring the line between
viruses
and worms.
Furthermore, some sources use
an alternative terminology in which a
virus
is any form of self-replicating
malware.
Some malware
are programmed to
damage the
computer by damaging programs, deleting
files, or
reformatting the hard disk. Other
malware programs are not designed to do any
damage, but simply replicate themselves and
perhaps make their presence known by
presenting text, video, or
audio messages. |
|
 |
Even these less sinister
malware programs can create problems for the
computer user. They typically take up
computer memory used by legitimate programs.
as a result, they often cause erratic
behavior and can result in system crashes.
In addition, much malware is bug-ridden, and
these bugs may lead to system crashes and
data loss. Many CiD programs are programs
that have been downloaded by the user and
pop up every so often. This results in
slowing down of the computer, but it is also
very difficult to find and stop the problem. |
|
Virus History:
The Creeper virus was first detected on aRPaNET, the forerunner
of the Internet in the early 1970s. It propagated via the
TENEX operating system and could make use of any connected modem
to dial out to remote computers and infect them. It would
display the message "I'M THE CREEPER : caTCH ME IF YOU caN�..
It
is possible that the Reaper program, which appeared shortly
after and sought out copies of the Creeper and deleted them, may
have been written by the creator of the Creeper in a fit of
regret. |
|
|
a common misconception is that a program called "Rother J" was
the first computer virus to appear "in the wild" � that is,
outside the single computer or lab where it was created, but
that claim is false. See the Timeline of notable computer
viruses and worms for other earlier viruses. It was however the
first virus to infect computers "in the home�. Written in 1982
by Richard Skrenta, it attached itself to the apple DOS 3.3
operating system and spread by floppy disk. This virus was
originally a joke, created by a high school student and put onto
a game on floppy disk. On its 50th use the Elk Cloner virus
would be activated, infecting the computer and displaying a
short poem beginning "Elk Cloner: The program with a
personality�.
The first
PC virus in the wild was a boot sector
virus called (c)brain, created in 1986 by
the Farooq alvi brothers, operating out of Lahore, Pakistan. The
brothers reportedly created the
virus to deter pirated copies of
software they had written. However, analysts have claimed that
the ashar virus, a variant of brain, possibly predated it based
on code within the
virus.
before
computer networks
became widespread, most viruses spread on removable media,
particularly floppy disks. In the early days of the personal
computer, many users regularly exchanged information and
programs on floppies. Some viruses spread by infecting programs
stored on these disks, while others installed themselves into
the disk boot sector, ensuring that they would be run when the
user booted the computer from the disk, usually inadvertently.
PCs of the era would attempt to boot first from a floppy if one
had been left in the drive. This was the most successful
infection strategy until floppy disks fell from favour, making
boot sector viruses the most common in the wild.
Traditional
computer viruses emerged in the
1980s, driven by the spread of
personal
computers and the resultant increase in bbS
and modem use, and software sharing.
bulletin board driven software sharing
contributed directly to the spread of
Trojan
horse programs, and
viruses were
written to infect popularly traded software. Shareware and
bootleg software were equally common vectors for
viruses on
bbS's.[citation needed] Within the "pirate scene" of hobbyists
trading illicit copies of retail software, traders in a hurry to
obtain the latest applications and games were easy targets for
viruses.
Since the mid-1990s, macro viruses have
become common. Most of these
viruses are written in the
scripting languages for Microsoft programs such as Word and
Excel. These
viruses spread in Microsoft Office by infecting
documents and spreadsheets. Since Word and Excel were also
available for Mac OS, most of these viruses were able to spread
on Macintosh computers as well. Most of these viruses did not
have the ability to send infected e-mail. Those viruses which
did spread through e-mail took advantage of the Microsoft
Outlook COM interface.
Macro viruses pose unique problems for
detection software. For example, some versions of Microsoft Word
allowed macros to replicate themselves with additional blank
lines. The virus
behaved identically but would be misidentified as a new virus.
In another example, if two macro viruses simultaneously infect a
document, the combination of the two, if also self-replicating,
can appear as a "mating" of the two and would likely be detected
as a virus unique from the "parents�.
a
virus may also send a web address link as
an instant message to all the contacts on an
infected machine. If the recipient, thinking
the link is from a friend (a trusted source)
follows the link to the website, the
virus
hosted at the site may be able to infect
this new computer and continue propagating.
The newest species of the
virus family is
the cross-site scripting
virus. The
virus emerged from research and
was academically demonstrated in 2005.This virus utilizes cross-site scripting
vulnerabilities to propagate. Since 2005
there have been multiple instances of the
cross-site scripting viruses in the wild,
most notable sites affected have been
MySpace and Yahoo.
Sources:www.wikipedia.com
Published by:
www.seekinusa.com
,
Tags:
computer virus,how
computer
viruses work,free
antivirus removal programs,virus
history,free
antivirus software protecting,free
antivirus ,computer
infected with virus,computer
virus,how
computer viruses work
|
|
|
|
|
|
|
