Bit,Byte and Character

 

Blog Diagram

Computer System

CHAPTER 2=COMPUTER SYSTEM

-SYSTEM CONCEPT

--OVERVIEW OF COMPUTER SYSTEM

-Define COMPUTER SYSTEMS.

Computer is an electronic device, operating under the control of instruction stored its 

own memory,

-that can accept data (input)

-process the data according to specified rules (process)

-produce result (output)

-and store the result for future use (storage)

State the MEANING THE INPUT, PROCESS, OUTPUT AND STORAGE.

Input=

-input is any data and instructions entered into the memory of a computer.

There are four types of input which are: text, graphics, audio and video.

Input device=

-Input device is any hardware component that allows user to enter data and instruction

into a computer.

 -e.g. keyboard, mouse, scanner, barcode reader

 -Also pointing devices: mouse, joystick, track ball, touch screen, pointing stick and

graphic tablet.

Processor/ CPU/ Central/ Processing Unit/ Microprocessor=

-CPU is an electronic component on a computer`s motherboard that interprets and

carries out the basic     instructions that operate the computer

-e.g. Intel Pentium IV, AMD Athlon, G4

Output=  

-Output is data that has been processed into a useful from, called information.

Output device=

-output device is any hardware component that present information (processed data)

to one or more people.

-e.g. Speaker, Monitor, LCD Projector, Printer and Plotter.

Storage=

-Storage is a location in which data, instructions, and information are saved for future use.

-e.g. CD ROM, diskette, hard disk.

SECURITY MEASURES

Security measures are measures taken as a precaution (taken beforehand)

against theft or espionage or sabotage or possible danger or failure. Usually

we use antivirus, cryptography, firewall and data backup to protect sensitive

information.

 Apply the correct security procedures. ANTIVIRUS, ANTI-

SPYWARE, CRPTOGRAPHY, FIREWALL, DATA BACKUP, 

AND HUMAN ASPECTS.

Anti-virus=

-is a utility program that the protects the computers against viruses by identifying

and removing computer viruses found in the computer memory, computer storage

or incoming e-mails files. Examples of antivirus are Norton Antivirus, AVG, Kaspersky, Bitdefender and Not32.

Anti-spyware=

-Is a utility program that protects the computers against spyware.

-Spyware is software or computer program that is designed secretly

record and report an individual`s activities on the internet. Spyware usually

enters your system through the internet, sometimes when you open e-mail or

download software especially shareware and freeware.

-Examples of anti-spyware program are Spybot Search and Destroy, Ad-aware 

and Spyware Blaster.

Firewall=

-A firewall is a software or hardware that secures a network, shielding, it from

access by unauthorized users.

-We use fire wall to prevent hacking (unauthorized access is the use of a computer

or network without permission)

Backup=

-Is utility program that makes a copy of all files or selected files that have been 

saved onto a disk.

-We backup our data to ensure that our data can still be used if the original is

corrupted and prevent our files from malicious program – virus, Trojan horse, 

worm, logic bomb, etc.

-Backup data is important when original data is corrupted.

Note: When data on a computer becomes corrupt, it is spoilt and cannot be 

properly used because it has become change in wrong ways.

Cryptography=

-Is a process of transforming plaintext into ciphertext then back againt.

-Encryption is a process of converting plaintext into ciphertext. Decryption 

is the process of converting ciphertext into plaintext.

-An encryption key is a formula that the sender of that the data uses to encrypt

plaintext. A decryption key is a formula that the recipient of the data uses to 

decrypt ciphertext.

-Until recently, encryption was used only by intelligence service, militaries, and banks.

We use cryptography to secure the information and prevent hacking or unauthorized

access.

Human aspects=

-Refer to the user and also the intruder of a computer system. Human aspect security

is the hardest aspects to give protection to. The most common problem of human aspect

security is the lack of achieving a good information security procedure.

SECURITY MEASURES

Security measures are measures taken as a precaution (taken beforehand)

against theft or espionage or sabotage or possible danger or failure. Usually

we use antivirus, cryptography, firewall and data backup to protect sensitive

information.

 Apply the correct security procedures. ANTIVIRUS, ANTI-

SPYWARE, CRPTOGRAPHY, FIREWALL, DATA BACKUP, 

AND HUMAN ASPECTS.

Anti-virus=

-is a utility program that the protects the computers against viruses by identifying

and removing computer viruses found in the computer memory, computer storage

or incoming e-mails files. Examples of antivirus are Norton Antivirus, AVG, Kaspersky, Bitdefender and Not32.

Anti-spyware=

-Is a utility program that protects the computers against spyware.

-Spyware is software or computer program that is designed secretly

record and report an individual`s activities on the internet. Spyware usually

enters your system through the internet, sometimes when you open e-mail or

download software especially shareware and freeware.

-Examples of anti-spyware program are Spybot Search and Destroy, Ad-aware 

and Spyware Blaster.

Firewall=

-A firewall is a software or hardware that secures a network, shielding, it from

access by unauthorized users.

-We use fire wall to prevent hacking (unauthorized access is the use of a computer

or network without permission)

Backup=

-Is utility program that makes a copy of all files or selected files that have been 

saved onto a disk.

-We backup our data to ensure that our data can still be used if the original is

corrupted and prevent our files from malicious program – virus, Trojan horse, 

worm, logic bomb, etc.

-Backup data is important when original data is corrupted.

Note: When data on a computer becomes corrupt, it is spoilt and cannot be 

properly used because it has become change in wrong ways.

Cryptography=

-Is a process of transforming plaintext into ciphertext then back againt.

-Encryption is a process of converting plaintext into ciphertext. Decryption 

is the process of converting ciphertext into plaintext.

-An encryption key is a formula that the sender of that the data uses to encrypt

plaintext. A decryption key is a formula that the recipient of the data uses to 

decrypt ciphertext.

-Until recently, encryption was used only by intelligence service, militaries, and banks.

We use cryptography to secure the information and prevent hacking or unauthorized

access.

COMPUTER SECURITY

3.0 COMPUTER SECURITY..

3.1 Define COMPUTER SECURITY

      Computer security means protecting our computer system and the information they contain unwanted                                                             access , damage, destruction or modification.

COMPUTER THREATS

3.2  Explain briefly the different COMPUTER THREATS to computer security: MALICIOUS CODE, HACKING, NATURAL DISASTER AND THEFT.

       I.            Malicious code

Malicious code is a computer program that perfume unauthorized process on a computer or network. There are various kinds of malicious code

Virus – A virus is a computer program that is designed to copy itself into the other programs stored in a computer. It attaches itself to the program usually capable of causing great harm to files or other programs on the same computer. A true virus cannot spread to another computer without human assistance.

The most dangerous computer viruses of the 20^th century.

                                                          a.            Morris – It could overwrite the Master Boot Record of the HDD, thus making it impossible for the uses to access the hard disk.

                                                          b.            CIH ( a . k . a Chernobyl) After being activated, the virus overwrote data on the HDD of the infected PC, making the letter inoperable. 

 

Trojan Horse – Trojan horse is a computer program that performs a useful task while the same time carry out
some secret desctrucive act. The contents of a trojan horse can be a virus or worm.

In Greek mythology, there is a story about the Trojan War. This war lasted many years, as the Greeks could 
not penetrate the heavily barricaded city or Troy. So one day, a few of the Greek soldiers brought the  people
of Troy a large wooden horse, which they accepted as a peace offering. The horse was moved inside the city
walls, where it sat until the night. After the people of the city had fallen asleep, Greek soldiers jump out of the
wooden horse, opened the gates to their fellow soldiers in, and took over the city.

A Trojan horse is a computer programs that acts as regular programs, such as game, disk utility, and even anti
virus program. But if it runs, this program can do malicious thing to your computer.

For example, a Trojan horse might appear to be a computer game, but once you double-click it, the program
starts writing over certain parts of your hard drive, corrupting your data.

The Zeus Trojan, called “most dangerous virus ever created” has stolen 675,000 from a British financial
institution. About 3,00 online banking customers have been victims of a computer virus attack that empties 
their accounts while showing them fake statements so the scam goes undetected.

 Logic bomb-A logic bomb is a computer virus or a worm that is designed to activated under certain
condition. An example of logic bomb is a time bomb. It goes out and causes threats at a specific time or date.
e.g

Friday the 13^th – each Friday 13^th it deletes all programs in the infected system.

Michelangelo – each march 6^th it overwrites the first on hundred sectors of the hard disk with nulls.

Trapdoor-and backdoor. Trapdoor is computer program that open the back door and allow other people to
have unauthorized access to your computer over internet. Backdoor functions can include: sending/receiving
files, launching/deleting files, executing files and deleting data.

Worm-A program that copies itself and spread through the network.

A computer infected by a virus, worm, or Trojan horse often has one or more of the following symthoms:

                                i.            Screen displays unusual message or image.

                              ii.            Music or unusual sound plays randomly.

                            iii.            Available memory is less than expected.

                            iv.            Existing programs and files disappear.

                              v.            Files become corrupted. 
Hacking

Hacking refer to unauthorized access to the computer system by a hacker. A hacker is a person who access a computer or network illegally. A hacker has advanced computer and network skills.

Nature Threats (Act of god)

Computers are also threatened by natural or environmental disaster. Examples of natural and environmental disasters are flood, fire, earthquakes, storm, tornados, excessive heat and inadequate power.

Theft

Two types of theft

                               a.            Computer is used to steal money, goods, information and resources.

                              b.            Stealing of computers especially notebook and PDA.

 Three approaches to prevent theft:

                              a.            Prevent access by using locks, smart card or password.

                              b.            Prevent portability by restricting the hard ware from being moved.

                              c.            Detect and guard all exits and record any hardware.