A computer virus is a type of malicious software or malware that attaches itself to other programs and files to replicate itself. Viruses can damage software, steal personal information, slow down systems, and more. Antivirus software uses techniques like on-access scanning, virus definitions, heuristics, and detection testing to identify and remove viruses and other malware from computers. Regularly updating antivirus software and virus definitions is important for protection.

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2. What is computerVirus?
 Malware, on the other hand, is a much broader
term. Malware is simply short for "malicious
software” and it is defined as any type of software
that does mischief or permanent damage to your
computer.
 A computer virus is a piece of malicious computer
code that attaches itself to a software program,
email or computer file which damages your
software, hardware or files.

3. What can virus do?
 Viruses can trick you into buying fake software,
steal your personal information and use it to get to
your money, or be sold on the digital equivalent of
the black market. Powerful viruses are valuable and
potentially lucrative tools.
 Damage Software
 Slow your system
 Can take Control
 Steal Information
 Damage Data

4.  Traditional computer viruses were first widely seen
in the late 1980s, and came about because of
several factors. The main factor was the spread
of personal computers (PCs)
 Early viruses were pieces of code embedded in a
larger, legitimate program, such as a game or
word processor.When the user downloads and
runs the legitimate program, it looks around to
see if it can find any other programs ,modifies the
program to add the virus's code into that
program.Then the virus launches the "real
program.".The virus has now reproduced itself, so
two programs are infected.

5. Types
 Spyware
 Virus
 Worms
 Trojan Horse
 Bots
 Rootkit
 Adware

6. Adware
 The term adware is frequently used to describe a
form of malware(malicious software) which
presents unwanted advertisements to the user of a
computer.The advertisements produced by adware
are sometimes in the form of a pop-up or
sometimes in an "uncloseable window".

7. Spyware
 Spyware is a type of malware that is installed on a
computer without the knowledge of the owner in
order to collect the owner’s private information
 Spyware is often hidden from the user in order to
gather information about internet interaction,
keystrokes ,passwords without the knowledge of
the owner in order to collect the owner’s private
information

8. Virus
 A virus is a small piece of software that piggybacks
on real programs. For example, a virus might attach
itself to a program such as a spreadsheet program.
Each time the spreadsheet program runs, the virus
runs, too, and it has the chance to reproduce (by
attaching to other programs) or wreak havoc.

9. Bots
 A "bot" is a type of malware that allows an attacker
to take control over an affected computer.Also
known as “Web robots”, bots are usually part of a
network of infected machines, known as a
“botnet”, which is typically made up of victim
machines that stretch across the globe.

10. Trojan Horse
 The files which contains this virus, claim to be
desirable programs, but they are malicious
 A very important distinction from true viruses is
that they do not replicate themselves, as viruses
do.Trojan horses contain a malicious code which,
when triggered, causes loss or theft of data

11. Worm
 A type of computer virus that can replicate itself
over a computer network and perform destructive
tasks such as using up computer memory
resources.
 Worms do not infect other files as viruses typically
do, but instead worms make copies of themselves
over and over depleting system resources (hard
drive space) or depleting bandwidth (by spreading
over shared network resources

12.  A self-replicating virus that does not alter files but
resides in active memory and duplicates itself. Most
worms are spread as attachments to emails. It is
common for worms to be noticed only when their
uncontrolled replication consumes system
resources, slowing or halting other tasks

13. Rootkit
 A rootkit is a type of software designed to hide the
fact that an operating system has been
compromised, sometimes by replacing vital
executables.
 Rootkits allow viruses and malware to “hide in plain
sight” by disguising as necessary files that your
antivirus software will overlook.
 Rootkits themselves are not harmful; they are
simply used to hide malware, bots and worms.

14. How to Identify virus
 First you need to determine if your computer has
a virus at all.You might suspect your computer of
having a virus if it seems to be sluggish.
 If yourWeb browser suddenly looks different or
automatically goes to a site you don't recognize,
that's a good indication that you've got some
malware.
 If your computer is unstable and crashes fairly
often, you may have a problem. And if you try to
access files but receive a message saying they're
corrupted, that's another sign.

15.  If you do think your computer has a virus, you need
to run antivirus software to weed it out. Some
viruses disable antivirus software -- they're clever
that way.
 A few malware variants will try to block you from
downloading antivirus software. If that's the case,
you may need to download the software on
another computer and transfer it to disk or a flash
drive.
How to protect from virus

16. Anti-virus
 An antivirus program is an essential part of a multi-
layered security strategy – even if you’re a smart
computer user, the constant stream of
vulnerabilities for browsers, plug-ins, and the
Windows operating system itself make antivirus
protection important.
 Antivirus programs are powerful pieces of software
that are essential onWindows computers.
 There are a lot anti-virus software available in the
market for purchase.

17. Types of Antivirus

18. On-Access Scanning
 Antivirus software runs in the background on your
computer, checking every file you open.This is
generally known as on-access scanning,
background scanning, resident scanning, real-time
protection, or something else, depending on your
antivirus program
 Antivirus programs also scan other types of files
that can contain viruses. For example, a .zip archive
file may contain compressed viruses, or aWord
document can contain a malicious macro.

19. Virus Definitions
 Your antivirus software relies on virus definitions to
detect malware.That’s why it automatically
downloads new, updated definition files – once a
day or even more often.
 The definition files contain signatures for viruses
and other malware that have been encountered in
the wild
 When an antivirus program scans a file and notices
that the file matches a known piece of malware, the
antivirus program stops the file from running,
putting it into “quarantine.” Depending on your
antivirus program’s settings, the antivirus program
may automatically delete the file

21. Heuristics
 Antivirus programs also employ heuristics.
Heuristics allow an antivirus program to identify
new or modified types of malware, even without
virus definition files.
 For example, if an antivirus program notices that a
program running on your system is trying to open
every EXE file on your system, infecting it by
writing a copy of the original program into it, the
antivirus program can detect this program as a
new, unknown type of virus.

22. Detection Rates
 Different antivirus programs have different
detection rates, which both virus definitions and
heuristics are involved in.
 AV-Comparative regularly releases studies that
compare the current state of antivirus detection
rates.The detection rates tend to fluctuate over
time – there’s no one best product that’s
consistently on top
 If you’re really looking to see just how effective an
antivirus program is and which are the best out
there, detection rate studies are the place to look.

23. AV-Comparative

24. Testing an Antivirus Program
 If you ever want to test whether an antivirus
program is working properly, you can use the EICAR
test file.
 The EICAR file is a standard way to test antivirus
programs – it isn’t actually dangerous, but antivirus
programs behave as if it’s dangerous, identifying it
as a virus.

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