Is a type of malware, designed to replicate
itself by copying itself into the other
programs stored in a computer. It may cause
a program to operate incorrectly or
corrupting a computer's memory.
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Software that is written and distributed for
malicious purposes, such as impairing or
destroying computer systems.
Characteristics of computer viruses
They are a piece of program or code.
Executes without any permission or informing to user.
Replicates, and made copies of themselves to spread.
Some types require special command to replicate.
can corrupt and distribute personal info of the user over internet.
They are all men made.
• Computer functions slower than normal
• Responds slowly and freezes often.
• Often restarts itself.
• See uncommon error messages, distorted menus,
and dialog boxes.
• Notice applications fail to work correctly.
• Fail to print correctly.
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History of computer virus
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john von Neumann came up with the theory about self-
replicating programs and “creeper” was the first
Virus invented for experimental purpose. 1981
Apple Viruses 1, 2, and 3 are some of the first viruses
in the public domain. Found on the Apple II operating
system, the viruses spread through computer games.
Fred Cohen, defines a computer virus as “a computer
program that can affect other computer programs by
modifying them in such a way as to include a (possibly
evolved) copy of itself.”
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the first PC virus, codename “The Brain” is released from
StrangeBrew is the first virus to infect Java files.
The Chernobyl virus spreads quickly via .exe files
the virus is quite destructive, attacking not only files but
also a certain chip within infected computers.
Tristate is the first multi-program macro virus; it infects
Word, Excel, and PowerPoint files.
“I Love You” virus appears. It managed to infect millions
of computers in just under a day.
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the Code Red virus posed a serious threat to the White House
website. It infected tens of thousands of computers
The same year, the Nimda virus hits the Internet. In the brief
history of computer viruses this is one of the most sophisticated
viruses ever to appear.
March saw the world's first cell phone virus: Commwarrior-A.
The virus probably originated in Russia, and it spread via text
Stuxnet is a computer worm targeting Siemens industrial
software through Microsoft Windows.
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TYPES OF COMPUTER VIRUSES
Logic and time bomb virus
ROLL NO: 11742
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• Email viruses first started showing up in the
1990s when the use of email became
• Email virus is of two types:
• Melissa virus
• ILOVEYOU virus
ROLL NO: 11742
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• One of the most impressive viruses to hit
computers was the Melissa virus, which
happened in March 1999.
ROLL NO: 11742
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• Another notable email virus was called the
ILOVEYOU virus, which infected computers
on May 4, 2000.
ROLL NO: 11742
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• A program that makes copies of itself; for
example, from one disk drive to another, or
by copying itself using email or another
ROLL NO: 11742
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A sector on the computer floppy disk drive, hard drive, or other bootable disk drive
that contains instructs the computer on how to boot from the drive.
There are two kinds of boot sectors - volume boot records and master boot records.
IBM PC disk drives:
IBM PC disk drive have different types of boot sectors
• MBR (master boot record) which is the first sector of a portioned hard drive volume boot
• VBR (volume boot record) which contains partition information at the beginning of each
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Example with the help of diagram:
In this example, the drive has two partitions; each partition contains its own VBR.
When BIOS hands control over to the boot sectors, the MBR takes control and starts
the boot process and refers to the VBR to point it to the partition information. Several
major kinds of boot sectors could be encountered on IBM PC compatible hard
disks, floppy disks and similar storage device.
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A boot sector virus is a computer virus that infects a storage device's
MBR. It is not mandatory that a boot sector virus successfully boot the
victim's PC to infect it. As a result, even non-bootable media can
trigger the spread of boot sector viruses. These viruses copy their
infected code either to the floppy disk's boot sector or to the hard
disk's partition table. During start-up, the virus gets loaded to the
computer's memory. As soon as the virus is saved to the memory, it
infects the non-infected disks used by the system.
The propagation of boot sector viruses has become very rare since the
decline of floppy disks.
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What does Boot Sector Virus mean?
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A logic bomb also called
because all that's left after it detonates is computer
slag, is not the same thing as a virus, although it often
behaves in a similar manner.
It is a piece of computer code that executes a
malicious task, such as:
•Clearing a hard drive
•Deleting specific files
It's secretly inserted into the code of a computer's
existing software, where it lies dormant until that event
This event can be either
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• written in a macro language
• spread as an e-mail virus
• depends on the application
rather than the operating system
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• "infects" a Microsoft Word or
• causes a sequence of actions
to be performed automatically
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Attachment Of Virus
Appearance Of Virus
Execution Or Running Of Effected Program
Computer System Get Effected With Virus
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There are literally dozens of ways for
viruses to enter into the computer system.
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Virus attaches to its target file or
software present in computer system .
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:It can appear in the form of code, scripts, active content, other software and email
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• “Antivirus" is protective
software designed to defend your
computer against malicious
software. Malicious software, or
"malware" includes: viruses,
Trojans, key loggers, hijackers,
dialers, and other code that
vandalizes or steals your
computer contents. In order to be
an effective defense, your
antivirus software needs to run in
the background at all times.
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• One of the most common reasons
for failures or problems in
computers is the lack of antivirus
software, or expired antivirus
• A few examples are provided
• Computer run slowly itself.
• Damage parts of the system or
how the system operates without
the owner's knowledge .
• Be used to steal personal details .
• receiving out unauthorized
messages / emails.
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HOW IT WORKS ?
• Anti virus software will
constantly monitor the
activity of all the programs.
• If any program tries to write
data on an executable file
the antivirus software will
flag the program having a
suspicious behavior means
the suspected programs will
be marked as virus.
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So What Does Antivirus
• Antivirus software is
the "policeman" at the
gate of a computer
system. It protects the
incoming threats and
seeks out, destroys and
warns of possible
threats to the system.
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New viruses are coming
out all the time. It is the
job of the antivirus
software to keep up
with the latest threats.
This is achieved by daily
updates of the antivirus
data base,its purpose is
to counteract the latest
threats to provide
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• Examples of common antivirus
programs include Norton
Antivirus, Kaspersky Anti-Virus,
and ZoneAlarm Antivirus.