The operating system is the most important program that runs a computer and acts as its "brain". It allows other programs to run and manages the computer's hardware and software. In contrast, a computer virus is a malicious program that can delete or corrupt data and interfere with normal operation. Some signs of a virus infection include a computer running slowly, freezing frequently, or restarting unexpectedly. Users can prevent viruses by using antivirus software, backing up files, avoiding suspicious email attachments, and only downloading from trusted sources.

1. Operating System vs. Virus
Introduction to Computers / Word Processing

2. Chap 2B: OS vs. Virus 2
Operating System is the most important
program that runs on a computer.
Operating System vs. Virus
It is considered as the “brain” of the
computer system.
It is used to run other programs such as
MS Office and all other programs installed in
the computer system.

3. Chap 2B: OS vs. Virus 3
Without the OS the computer system is
practically useless.
Operating System vs. Virus
On the other hand, a computer virus is
a computer program that disturbs or interfere
the smooth operation of the computer system.
It can delete or corrupt computer data,
thus nobody wants this program inside the
computer system.

4. Chap 2B: OS vs. Virus 4
Operating System
The OS is the manager of all the computer
system’s hardware and software.
In layman’s term, the OS is a computer program
that provides an interface for the user to
communicate with the computer.
Operating system is a collection of
programs that controls how the CPU, memory,
and I/O devices work together.

5. Chap 2B: OS vs. Virus 5
Operating System
 Organizes and manages files and directories.
 Controls how data and instructions are
loaded and executed by the CPU.
 Coordinates the CPU, memory, and
peripheral devices.
Some of the functions of an OS:
 Recognizes input from the keyboard and
sends output to the display screen.

6. Chap 2B: OS vs. Virus 6
Primary Purpose of an OS:
Operating System
Maximize the productivity of a computer
system by operating in the most efficient
manner and minimizing the amount of human
intervention.

7. Chap 2B: OS vs. Virus 7
Operating System
Most modern OSes utilizes a user
interface to make interacting with the
computer easy.
The goal of user interface is to be “user-
friendly”, which means that the software can
be used easily by individuals with limited
training.

8. Chap 2B: OS vs. Virus 8
Operating System
- it utilizes windows, icons, menus, and
pointers.
Graphical User Interface (GUI)
- a user interface that displays graphics in
addition to text when it communicates with
the user.

9. Chap 2B: OS vs. Virus 9
USERS
Operating System
DISK
CPU
NETWORK
APPLICATION
PROGRAMS
I/O
DEVICES
OS
(NUCLEUS)

10. Chap 2B: OS vs. Virus 10
A computer virus is a small self-
duplicating computer program that attaches
itself to some other program and spreads from
one computer to another, interfering with
computer operation.
Computer Virus
 It can use an e-mail program to spread the
virus to other computers
 It can delete everything on the hard disk.

11. Chap 2B: OS vs. Virus 11
How do computer viruses infection occur?
 They most easily spread by attachments in
e-mail messages.
Computer Virus
 It can arrive on a flash drives.
 Computer viruses also spread by using
downloads on the Internet.

12. Chap 2B: OS vs. Virus 12
 The computer runs slower than usual.
Computer Virus Indicators
Primary indicators of computer virus infection:
 The computer stops responding, or it locks up
frequently.
 The computer restarts on its own every few
minutes and does not run as usual.
 Computer applications do not work correctly.
 Disks or disk drives are inaccessible.

13. Chap 2B: OS vs. Virus 13
Computer Virus Indicators
 There’s a double extension on attachment
that’s recently opened (e.g. .jpg, .gif, or .exe).
 Antivirus program cannot be restarted or is
disabled for no reason.
 Antivirus program cannot be installed or won’t
run on the computer.
 New icons appear on the desktop that are not
placed there or not even associated with any
recently installed programs.

14. Chap 2B: OS vs. Virus 14
1949, John von Neumann proposed that it was
theoretically possible for a computer
program to replicate.
1950s, the theory was tested at Bell
Laboratories through the development of
Core Wars, where players created tiny
computer programs that attacked, erased,
and tried to propagate on an opponent's
system.
Origin of Computer Virus

15. Chap 2B: OS vs. Virus 15
1985, the first Trojan horses appeared, posing
as a graphics-enhancing program called
EGABTR and as a game called NUKE-LA.
Origin of Computer Virus
1986, the Brain virus appeared and spread
worldwide by 1987.
1983, American Electrical Engineer Fred
Cohen, coined the term virus to describe a
self-replicating computer program.

16. Chap 2B: OS vs. Virus 16
1988, two new viruses appeared: the Stone
virus, and Internet worm.
1989, the Dark Avenger, the first fast infector
virus, followed by the first Polymorphic
virus in 1990.
Origin of Computer Virus
1995, the WinWord Concept virus, was
created.

17. Chap 2B: OS vs. Virus 17
1999, the Melissa macro virus, which costs
corporations millions of dollars due to
computer downtime and lost productivity.
Origin of Computer Virus
2000, the VBS_LOVELETTER virus, a.k.a. the
Love Bug and the ILOVEYOU virus in
which losses were estimated at $10 billion,
with a 1:5 ratio of infection.

18. Chap 2B: OS vs. Virus 18
History of Computer Virus
2003, the SoBig worm, considered as the
fastest spreading virus, capable of sending
massive amounts of junk e-mail or spam.
2003, the Blaster worm infected more than 10
million machines worldwide that lacked the
appropriate patch (software bug corrector).
January 2004, the MyDoom virus set a new
record, spreading even faster than SoBig,
causing even more damage.

19. Chap 2B: OS vs. Virus 19
Applying anti-virus measures is the best
way to protect users against viruses.
Anti-virus Measures
1. Make backups of all software (including OS)
 If a virus attack occurs, safe copies of your
files and software can be retrieved.
2. Have anti-virus software installed and
updated regularly.
 This is to detect, report and (where
appropriate) disinfect viruses.

20. Chap 2B: OS vs. Virus 20
Anti-virus Measures
3. Inform all users that the risk of infection
grows exponentially.
4. Contact a Computer Professional for
analysis.
 When people exchange flash drives,
download web material or open email
attachments without caution.
 If in doubt of any suspicious item that anti-
virus software does not recognize.

21. Chap 2B: OS vs. Virus 21
Best practices for detecting and preventing
viruses.
Computer Virus Prevention
1. Do not open any files attached to an email
from an unknown, or untrustworthy source or
even if it appears to come from someone you
know if the subject line is questionable.
 If the need to do so is there, always save
the file to your hard drive before doing so.

22. Chap 2B: OS vs. Virus 22
Computer Virus Prevention
2. Delete chain emails and junk email.
 Do not forward or reply to any to them.
These types of email are considered
spam, which is unsolicited, intrusive mail
that clogs up the network.
3. Exercise caution when downloading files
from the Internet.
 Ensure that the source is a legitimate and
reputable one.

23. Chap 2B: OS vs. Virus 23
Computer Virus Prevention
4. When in doubt, always err on the side of
caution.
 Do not open, download, or execute any
files or email attachments.
 Not executing is the most important of
these.

24. Chap 2B: OS vs. Virus 24
 Click to add subtitle
End