1. CHAPTER 1: INFORMATION
AND COMMUNICATION
TECHNOLOGY
Computer security

2. Computer Security
Means protecting our computer system and the
information they contains against unwanted access,
damage, destruction or modification.

3. Computer Threads
Malicious code
 Is a computer program that perform unauthorized processed an a
computer or network
 There are various kinds of malicious code:
i) Virus
ii) Trojan horse
iii) Logic bomb
iv) Trapdoor
v) Worm
 Differences between worm and virus are:
WORM VIRUS
Operates through the network Spreads through any medium
Spread copies of itself as a stand alone Spread copies of itself as a program
program that attaches to other program

4.  A computer infected by a virus, worm or trojan
horse has one or more of the following symptoms:
 Screen displays unusual message or image
 Music or unusual sound plays randomly
 Available memory is less than expected
 Existing programs and files disappear
 Files become corrupted

5. Hacking
 Hacking refer to unauthorized access to the
computer system by a hacker
 A hacker is a person who accessed a computer or
network illegally
 A cracker also is someone who accessed a
computer or network illegally but has to intend of
destroying data, stealing information or other
malicious action

6. Nature threads
 Computers are threatened by natural or
environmental disaster. Be it at home, stores, offices
and also automobiles
 Examples: flood, fire, earthquakes, storms,
tornados, excessive heat and inadequate power

7. Theft
 Two types of theft
i) Computer is used to steal money, goods, information
and resources
ii) Stealing of computers especially notebook and PDA
 3 approaches to prevent theft:
i) Prevent access by using locks, smart card or
password
ii) Prevent portability by restricting the hardware from
being moved
iii) Detect and guard all exits and record any hardware

8. Security Measures
 Security measures are measures taken as a
precaution against theft or espionage or sabotage
or possible danger or failure
 Usually we use antivirus, cryptography, firewall and
data backup to protect sensitive information

9. Anti-virus
 Is a utility program that we use to protect a computer
against viruses by identifying and removing computer
viruses found in the computer memory, computer storage or
incoming e-mails files
 Examples:
Norton Antivirus
AVG
Kaspersky
Bitdefender
Nod32

10. Anti-spyware
 Is a utility program that we use to protect the
computers from spyware
 Spyware is a software or computer program that is
designed secretly record and report an individual’s
activities on the Internet
 Examples:
Spybot Search and Destroy
Ad-ware
Spyware Blaster

11. Firewall
 Is a piece of hardware or software which functions in
a networked environment to prevent some
communications forbidden by security policy
 We use firewall to prevent hacking (access is the
use of a computer or network without permission)
Types of firewall
SCREENING ROUTERS PROXY GATEWAY GUARD
 simplest • some what complex • most complex
 sees only addresses and • sees full text of • sees full text of
service protocol type communication communication

12. Backup
 Is a utility program that makes copy of all files that
have been saved onto a disk
 Backup data is important when original data is
corrupted
 When data corrupted, it is spoilt and cannot be
properly used because it has become changed in
wrong ways

13. Cryptography
 Is a process of transforming plaintext into cipheart
then back again
 Encryption is a process of converting plaintext into
cipertext. Decryption is the process of converting
ciphertext into plaintext
 Encryption was used only by intelligence services,
militaries and banks. We use cryptography to
secure the information and prevent hacking or
unauthorized access.

14. plaintext encrypt ciphertext
plaintext decrypt ciphertext

15. Human aspects
 The user and also the intruder of a computer system
 The hardest aspects to give protection
 The most common problem of human aspect security
is the lack of achieving a good information
security procedure