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• Are machines that can store, retrieve and process information

• Include the following characteristics:– respond to specific instructions in a precise

manner

– can perform a prerecorded set of instructions

– able to store and retrieve large amounts of information

– use operating systems to function effectively

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• Break down into the five main following types:1. personal computer (PC): small, single-

user computer; used in homes and businesses; based on a microprocessorEx. desktop, laptop

2. work station: powerful, single-user computer; more powerful microprocessor than PCs

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Microprocessor: a chip that is the master control circuit of a computer CPU

3. minicomputer: a multi-user computer designed to handle hundreds of users at the same time

4. mainframe: a powerful, multi-user computer; can support hundreds or thousands of users simultaneously

5. supercomputer: an extremely fast computer; can perform hundreds of millions of instructions every second

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• Are programs that act as a translator between a computer user and the computer itself

• Control and manage all other programs that a computer contains

• Are the master program that makes everything else run

• Can be considered the core software on a computer that links the hardware, software and the computer user

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Hardware: the physical and mechanical components of a computer such as: monitor, mouse, chips, keyboard, etc.

Software: programs that direct the operation of computers; instructions for a computer

• Include the following four general types:1. real time operating systems (RTOS)

2. single-user, single task operating systems

3. single-user, multi-tasking operating systems

4. multi-user operating systems

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• Are used to control the following:– machinery– scientific tools– industrial instruments

• Do not allow the user to have much control over the system

• Are used for real-time applications such as: thermostats, mobile phones, spacecrafts, etc.

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• Allow users to do only one thing at any given time

• Are simple systems that would not be very efficient in the business environment

• Include Personal Digital Assistants or PDAs, Leap Frog, DS– small, handheld computers that only allow

users to operate one application at a time

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• Are the most common type of system found on PCs

• Allow the user to run several computer applications at the same time

• Include Windows (Microsoft) and Macintosh (Apple) platforms

• Uses GUI

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• Allows users to operate computers without knowing the language used to communicate with an operating system

• Makes computers much more efficient

• Eases the complications of operating a computer

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• Utilizes the following tools:

1. pointer: a symbol (usually an arrow) on a computer screen used to select objects

2. pointing device: an object such as a mouse used for pointing

3. icons: small pictures on a computer screen that represent programs and applications

4. desktop: an area on a display screen where icons are displayed

5. windows: divide the screen into different area so that several programs can run at the same time

6. menus: allow users to select commands from a list of choices

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• Allow multiple users to simultaneously use the programs on a single computer

• Should only allow users who have the necessary knowledge to use the system

• Are complex systems that require a lot of upkeep and maintenance

Examples: PS4, XBoxOne

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Computer Programmer: a person who designs, writes and installs computer programs and applications

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• Is a system for communication between two or more computers

• Enables users to share information and devices through the system

• Allows users to exchange software, hardware and other data

• Uses a cable or wireless connection to run

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• Connect computers without the use of wires and cables

• Uses electromagnetic waves to transmit information

• Are also used for telephones that are not connected to the wall

– example: cordless phones and cellular phones

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Electromagnetic Waves: a method of travel for information from computer to computer; consists of light waves, radio waves, microwaves, etc.

• Break down into the following main types– Local Area Network– Wide Area Network– Personal Area Network

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• Are local, privately owned networks• Have a high speed and low error rate• Are able to be measured in meters because

of their small geographical size • Typically means that the computers in the

network are within the same building or office

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Error Rate: the number of times an area network does not function properly compared to the total number of times the network is accessed

• Are networks that provide connections between computers in multiple locations

• Cover a significantly larger area than LANs

• Can be used to connect different office locations of a large company

• Consist of several LANs linked together to create a larger network

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• Usually cover the small area around a user’s workspace

• Allow users to transfer files and gain access to printers and other nearby hardware

• Cover a range of up to 10 meters in distance

• Used to connect devices that a single person uses with their computer

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• Is a worldwide, publicly accessed network • Allows interconnected computer networks

to transmit data back and forth• Enables contact between companies,

individuals, academic institutions, etc.• Consists of approximately 60,000

independent networks and 350 million active users

• Is doubling in size each year

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• Allows users to send messages from one computer to another through the Internet

• Is a quick, easy and efficient way to send and retrieve data

• Utilizes programs such as– AOL instant messenger– online chat rooms– e-mail

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• Allows multiple users to access the same equipment such as fax machines, printers or common files stored in one central place

• Are used so that several people can access the Internet and other computer programs simultaneously

• Can be used interchangeably with the names client-servers or network servers

• Store an abundant amount of information• Manage the resources of a network of

computers

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• Serve as a security device between a computer and Internet sites or between multiple computer networks

• Inspect network traffic passing between computer networks

• Shield networks from unauthorized visits

• Can also restrict unwanted data from flowing outside of a network

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• Serves as a unique identification for a computer on a network

• Helps distinguish individual computers since there are millions on the Internet these days

• Is a 32 bit code that is made up of four subsets of numbers

• Determines where information needs to be delivered

• Serves the same purpose as a street address– Example: (172.16.122.204)

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• Is a malicious computer program created by a user with objectives to harm or steal another’s property

• Is also referred to as Malware• Is important for users to be aware of

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• Is a piece of code attaching itself to a larger, more frequently used program – it then modifies the program– this is referred to as “piggybacking”

• Is active and running only when the host program is active

• Is designed to multiply and infect other programs the computer runs

• Protect themselves by hiding in a host program

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Host Program: a large, frequently run program attached to the virus

Piggybacking: the act of a computer virus attaching itself to another computer program

• Begins to carry out whatever malicious activity it is supposed to, once it has multiplied and infected other programs– the malicious activity is known as the payload

• Can spread fast, slow or not spread at all– if the virus programmer made an error in designing

the virus then it will not spread at all

• Can remain dormant in a computer until a specified time

• Can delete all data and files on a computer

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• Can affect different parts of the computer– such as:

• the hard drive• a CD/DVD Drive• any type of storage device

• Can spread through virtually any computer to server or computer to computer contact– Examples of spreading medians: 

• Internet• downloading attachments or music• CD or USB drive 31

• Is an independent program – Which multiplies itself by copying a

segment of itself unto another.

• Is classified by two types:– a network worm– a host worm

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• Can contain malicious instructions to hinder a computer’s performance

• Uses flaws or holes in the network to gain access to individual computers– this gives worms the ability to move

extremely fast through a network infecting computers• it could possibly infect an entire network of

computers within seconds

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• Multiplies by copying a segment of itself onto another computer over a network– the segments of the worm, on various computers

in a network, remain in contact with each other– if one segment of the worm fails or is removed,

then the other remaining segments must find another computer, prepare it for the worm and then add the segment to the rest of the worm

– this is how the worm moves through a network

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• Is completely contained on one running computer

• Copies itself to another computer through a network

• Deletes itself from the original computer, once it has moved to another computer

• Does not fragment or segment itself – a network worm does run different segments of

itself on different computers

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• Is a malicious program disguised in a seemingly innocent program

• Is an analogy referencing the “Trojan Horse” used by the Greeks to obtain access to the city of Troy– The Greeks were losing in the battle to overtake the city of Troy, so

their leader Odysseus, built a seemingly innocent giant wooden horse with a hollow belly, large enough for soldiers to hide in. He offered it to the Trojans as a sign of peace. The Trojans accepted the gift and celebrated their victory. Then at night while they were sleeping, the Greeks snuck out of the horse, which they were hiding in, and took the city of Troy.

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• Will generally gain access to administrative areas on a computer– once it has gained access to these areas, it will

create a back door– this gives the creator of the Trojan horse

unauthorized access to the user’s computer and the information it contains

• Will sometimes monitor keystrokes and browsing activity– this information is sent to companies sending the

user content and information they did not request• Can be discreet

– meaning they do not leave any trace of their presence

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• Began in 1949 when John Von Neumann wrote a paper called “Theory and Organization of Complicated Automata”– this paper assumed a computer program

could self-replicate– this theory was later called “Core Wars”

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• Became a reality in 1982 when the first virus called the “Elk Cloner” was created by Rich Skrenta– The virus created by Skrenta was created as a

prank on his friends. He modified floppy disks containing games or software which were swapped within his group of friends. Instead of running the software or game the disk displayed taunting messages.

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• Was created as what is now known as a boot sector virus– a copy of the virus is downloaded off of a disk

when the computer is booted up– then when someone else inserts a disk into the

computer, the virus is downloaded to the new disk • Began as an innocent prank

– however this prank opened the door for numerous, harmful viruses to be created

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• Progressed in the 80’s and 90’s, when hackers developed new ways to steal information and inhibit regular computer use

• Took significant strides with the following viruses:– “The Brain” in 1986 created in Pakistan by

brothers Basit Amjad and Farooq Alvi• this was a boot sector virus and technically the

first stealth virus, which means if anyone attempted to view the infected sector, the virus would replace it with the clean, original version of the sector

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• Stealth Virus: a virus in which if anyone attempts to view an infected sector, the virus will replace it with the clean, original version of the sector

• Boot Sector Virus: a virus which copies itself onto a computer off of a disk when the computer is booted up; then when someone else inserts a disk into the computer, the virus is downloaded to the new disk

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• Has been developed by hackers experimenting with other ideas of viruses and then building on them

• Was greatly effected by the “Vienna Virus”– this virus was picked apart by

Ralph Burger– he then wrote a book called

Computer Viruses: A High Tech Disease

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• Was created by Robert Morris in 1988• Was the first worm to be distributed over a

network without other users being aware of its presence

• Was designed for experimental purposes• Was released onto a network to remain

present without negatively affecting the network

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• Began clogging the network– by multiple versions of the worm being run on the

same machine at once– this slowed the system by using all of its

processing power, and inhibited new users from accessing the network

– Robert Morris went on trial and was convicted and received a fine, probation and community service

• Affected approximately 6,000 servers and caused between $10 million to $100 million dollars worth of damage

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• Are at both the state and federal level– meaning a hacker can be prosecuted at the state

level if the virus did not leave the state or at the federal level if it crossed state boundaries

• if it is prosecuted at the federal level the U.S. Secret Service will generally investigate

• Are usually considered a felony• Can be found on

http://www.ncsl.org/programs/lis/cip/viruslaws.htm– this is for individual state legislation

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• Began in 1986 with the Computer Fraud and Abuse Act– this lays out the prosecution for using the

computer for fraud– the punishment varies depending on:

• the amount of damage caused by the worm• if the amount of damage caused was intentional

– this would be difficult to find evidence• if the worm or virus was created for commercial

advantage or personal financial gain– the punishment for such a crime is

imprisonment for up to 20 years and/or a fine

• the fine is decided by a judge47

• Against computer worms and viruses comes from anti-virus software and good judgment from the computer user– use good judgment when opening suspicious e-

mails or downloading attachments• if it really does not look important, then do not

open it• viruses in e-mails can find a user’s e-mail list

then send itself in an attachment to all of the contacts on the list

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• May be completed by scanning all disks and files used on another computer before opening files– this is an easy feature contained in anti-virus

software• Requires users to scan attachments and downloads

from the Internet by an anti-virus software before opening them

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• Calls for users in a computer lab to clean up or “reboot” a computer before using – this can be done with a simple action

called Disk Cleanup• it can be found by going to Start>All

Programs>Accessories>System Tools> Disk Cleanup

• this removes all potentially harmful temporary Internet files

– also be sure to log out when using a public computer

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• Requires users to back up all important information periodically– in case a virus or worm does destroy all files

contained on a computer• Involves users to advise caution when

accepting copied software– sometimes software will be considered public

domain, where the manufacturer will give it to users at little or no cost

– be sure the copied software is from a trusted source

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• Is the most common form of computer protection against viruses and worms

• Was first introduced in 1990• Needs to be high-quality

– there is free anti-virus software on the Internet which will not protect a user’s computer as well as a program paid for

• Needs to updated regularly – most software will update itself regularly when

connected to the Internet, be sure to install all updates possible

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• Recommended for Windows® includes:– McAfee VirusScan®

– Norton AntiVirus®

• Recommended for Mac® includes:– McAfee Virex®

– Intego VirusBarrier®

– Norton AntiVirus®

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1. Do not use the computer during a storm.

2. Do not spray the computer with household cleanser to clean.

3. Do not spill liquids on the computer.

4. Keep the computer dust free.

5. Install one program, then test your computer before installing another.

6. Downloading from Internet sites could expose you computer to dangerous viruses.

7. Surge protectors help guard against lightning, but do not give complete protection.

8. You should remove the computer cover periodically (once a year) to clean inside.

9. Opening an email attachment could download a virus into your computer system.

10. Canned air should be used to clean your computer keyboard.

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