Short-Cut Keys of ComputerWindows Shortcut : |
Internet Organizations
- ISPs (Internet Service Providers) - They provide the connection to the internet for users and also provide routers that direct internet traffic.
- Corporations or Web hosting providers with mail servers and web servers - They provide the information posted on the internet and virtual data connections to other mail servers.
There are also other organizations that regulate the internet, providing communication standards and designing new communication standards for improvements. These communication standards are also known as protocols.
Summary
So the internet is a collection of organizations that provide equipment that support the internet functions and services. The internet connects many corporate and organizational private networks together thus enabling all these organizations to easily communicate.
Accessing the Internet
People use an internet browser to access web pages that are available across the internet. Internet browsers include Microsoft Internet Explorer, Netscape Navigator, Mozilla, and others.
Web pages are created in a marked up form of text file called HTML (Hyper-Text Markup Language). The markup within the text indicates document structure showing where paragraphs begin and end, what items are in a list, headers, tables and other document structure.
When people are browsing of surfing the internet, they usually go from place to place by clicking on links. These links are locations for specific pages and indicate the three things:
- Protocol being used such as http or ftp
- The domain that the web page is found on. This will point to a specific organization's or company's web server.
- The location of the page on the server including the directory path and file name.
An example link is "http://www.comptechdoc.org/basics/bastutorial/osintro.html". In this case http is the protocol being used, the comptechdoc.org domain indicates where the organization's web server is, and the "/basics/bastutorial/osintro.html" part of the string indicates the folders the file is in and the name of the file.
These links are sometimes called hyperlinks or URLs (Uniform Resource Locators)
The drawing below shows a typical layout of the components inside your computer case.
****************************OnlineSAB Cyber 'n' Communication*************************
What is a Network?The word network can be used to describe a very large and complicated set of equipment. In its most accurate and simplest definition a network refers to the cables and electronic components that amplify the signals going through the cables. The amplifying equipment is necessary to ensure accurate communication and make the signal stronger if it needs to go long distances.Broader DefinitionWhen many people talk about a network, they are talking about a network using a very broad concept. For instance if someone cannot get to their email, they may say "the network is down". Likewise they may say this if they cannot surf the internet or get to their files. They may not stop to think that in each specific instance there is a single piece of equipment that may provide the capability which they are trying to use.Most people who work on a corporate or organizational network think about the network in component parts. The three main parts are:
|
Services
Services include:
- Email service
- File service - Allows users to use and share file space on a computer with a lot of file space.
- Print service - Allows printing to printers connected on the network.
- Web surfing - Allowing someone to open web pages and see web sites on the internet.
- Filtering out undesired sites on the internet.
- Allowing someone to access the network from the outside (from home).
- Updating virus definitions on workstations.
- Allowing someone to log onto the network.
- Even giving a workstation an address on the network is a service. If your computer does not have an address, it cannot access the internet or any other resource on the network.
A Typical Network
A typical corporate or organizational network is shown below:
Of course there are variations on this network layout and some details have been left out for the sake of simplicity but this drawing should give you some idea about what goes on behind the scene on the network at your organization. Some servers and server functions have not been shown here.
The firewall is the device that protects all computers in the network from many attacks. It allows some types of network traffic into the network from the outside, but usually only for mail or web services. Usually the internet traffic that that is allowed to come into the network is routed to the part of the network labeled "DMZ" on the right side of the diagram. DMZ stands for demilitarized zone and is also called a semi-private network. In this DMZ is a web server which is used to allow people surfing on the internet to see web pages posted by the organization. A mail server is also shown in the DMZ but this could be replaced by a mail relay server while the mail server is placed inside the private network. The mail relay server would forward mail traffic from the outside to the mail server. This would increase the security of the network since a direct connection from the internet to the mail server would not be allowed.
The private network is of course the most secure part of the network. There are several servers on this network including:
- A login server (called a domain controller) which controls everyones permissions and access to the network resources such as files. Without this server, they cannot login to the network.
- An address server (called a DHCP server) which provides addresses to computers on the network so they can communicate as discussed earlier.
- A file server which provides common files and a private folder for users.
- A remote access server which allows users to connect to the network by telephone from the outside.
Also the workstations are part of this network.
Conclusion
Knowing the above information, if someone cannot get their mail, they may think the network is down. This is not likely to be the case. The mail server may be down but the network is not likely to be down. The same goes for when someone can't surf the web. There may be a problem with the firewall or the line connecting to the internet, but it is unlikely that the whold netwlrk is down. When problems are noticed it is best for the user to describe what they were trying to do and what happened.
****************************OnlineSAB Cyber 'n' Communication*************************
HardwareThe term hardware describes the physical parts of your computer which you can physically touch or see such as your monitor, case, disk drives, microprocessor and other physical parts.SoftwareThe term software describes the programs that run on your system. This includes your computer operating system and other computer programs which run. Software is written in a computer language (such as Basic, C, Java, or others) by programmers. The computer language is in a text format and can be read by a person although if you do not understand the structure and rules of the language you may not understand it very well. Once a program is written, an operation is performed on it which is called compiling. Compiling is the process of changing the textual written language into a binary language which can be understood by the computer.Writing these text files and converting them to computer readable files is the way operating systems and most application programs are created. BIOS (Basic Input/Output System)BIOS is a low level program used by your system to interface to computer devices such as your video card, keyboard, mouse, hard drive, and other devices. What BIOS programs provide in the computer are very simple function calls or small subprograms which can be used by higher level programs to perform simple operations on computer devices. For example a BIOS program would provide the ability to write a character to memory on a video card. |
BIOS is normally written in a low level computer language and is permanently or semi-permanently written into the computer system. This type of computer program is commonly referred to as firmware since it was historically written permanently into computer systems. Although BIOS is a program, because of its permanent state, it was not quite considered to be software so the term firmware is used to describe it.
Historically BIOS programs were written into a type of memory called ROM (read only memory). This type of memory would not lose its data when the computer lost power thus ensuring these BIOS programs would always be available. There were different variants of ROM memory some of which could be written multiple times but this memory could not normally be changed or re-programmed once the computer system was sold to the customer. Once ROM memory was written to, it could not be written to again and could only be read when in the possession of the customer. In more recent years a more flexible form of memory was developed called flash ROM which allows ROM memory to be written to after the computer system is in possession of the customer.
****************************OnlineSAB Cyber 'n' Communication*************************
Computer DataTo help understand computers it is best to first learn about computer data. Computer data is information required by the computer to be able to operate. It is used to:
Data StructureComputer data is in what is called binary format. This means that it is always a 0 or a 1. It only has these two states and must be in one of them.There are several fundamental data units which include:
|
Data transmission
Data transmission is the act of sending data from one place to another. Data is transmitted both inside and outside your computer. There are two fundamental methods of data transmission.
- Serial - Data is sent on a single line and one bit is sent at at a time. This is similar to a line which one item must come one after another.
- Parallel - Data is sent on more than one line at a time. This may be any number of bits at a time, but is usually one word at a time (two bytes) or possibly three bytes at a time.
****************************OnlineSAB Cyber 'n' Communication*************************
Computer HardwareThe term computer hardware refers to the various electronic components that are required for you to use a computer along with the hardware components inside the computer case. As you know your computer equipment is made of several common components. These include:
|
The Main Computer Box
The main computer box is made of several computer hardware components and subcomponents which include:- The case - The outside component which provides protection for the parts inside and provides a fan and power supply which are used to both cool the working parts inside and provide power to them.
- The motherboard - Hold the following computer hardware subcomponents:
- Memory - Used to provide temporary storage of information as discussed earlier.
- Microprocessor - Used to provide the processing of data function as discussed earlier.
- Video interface card which is also called the video card - This card is an interface between the computer monitor and the motherboard and its subcomponents such as the microprocessor and memory. This card may be included as part of the motherboard or it may plug into a card slot on the motherboard.
- Sound card is an interface between the computer speakers and the motherboard and its subcomponents such as the microprocessor and memory. This card may be included as part of the motherboard or it may plug into a card slot on the motherboard.
- One or more permanent storage devices some of which may be optional:
- Hard disk - Most computers today have a hard disk (sometimes called hard drives) which is the component most commonly used to provide permanent storage of data. Hard disks are usually permanantly installed in a computer.
- CD ROM drive or DVD drive - Used to provide permanant storage of data but this type of drive is used to bring information into the computer more commonly than it is used to store information from the computer. Sometimes this type of drive is used to back up data from the hard drive so data is not lost if a hard drive breaks. A DVD drive holds more data than a CD ROM drive and DVDs have enough storage capacity that they may be used to play or store movies. The storage media, the CD ROM or DVD may be removed from the computer.
- Floppy Drive - A low capacity storage device which can be written to as easily as it is read. The floppy disk may be easily removed from the computer. It is called a floppy because the part of the media that holds the data is on a material that is not rigid but it is enclosed in a more rigit case to give it durability.
The Case
The drawing below shows a typical case. It may help you understand where your connections for your monitor, keyboard, mouse, and other devices are if you should need to hook them up. For more specific information you should refer to your computer owner's manual.****************************OnlineSAB Cyber 'n' Communication*************************
What is a Virus?
A computer virus is a programme, or piece of code, that is written to interfere with, and harm, your machine. A virus can replicate itself, spread to other computers, and attack other programmes on your computer. (By attack, we mean change or delete files.) Computer experts distinguish between a virus, a worm, and a Trojan. Here's the differences:
Virus - Can replicate and spread to other computers. Also attacks other programmes
Worm - A special type of virus that can replicate and spread, but generally doesn't attack other programmes
Trojan - Doesn't replicate, but can spread. Doesn't attack other programmes. Usually just a way of recording and reporting what you do on your PC
Viruses are split into different categories, depending on what they do. Here are a few categories of viruses:
Boot Sector Virus
The Boot Sector of a PC is a part of your computer that gets accessed first when you turn it on. It tells Windows what to do and what to load. It's like a "Things To Do" list. The Boot Sector is also known as the Master Boot Record. A boot sector virus is designed to attack this, causing your PC to refuse to start at all!
File Virus
A file virus, as its name suggests, attacks files on your computer. Also attacks entire programmes, though.
Macro Virus
These types of virus are written specifically to infect Microsoft Office documents (Word, Excel PowerPoint, etc.) A Word document can contain a Macro Virus. You usually need to open a document in an Microsoft Office application before the virus can do any harm.
Multipartite Virus
A multipartite virus is designed to infect both the boot sector and files on your computer
Polymorphic Virus
This type of virus alter their own code when they infect another computer. They do this to try and avoid detection by anti-virus programmes.
You can also get viruses by downloading programmes from the internet. That great piece of freeware you spotted from an obscure site may not be so great after all. It could well be infecting your PC as the main programme is installing. And if you or your children download software from peer to peer networks (like Kazaa, Morpheus, Shareaza) then you could be downloading more than you bargained for!
If your PC is running any version of Windows, and it hasn't got all the latest patches and updates, then your computer will be attacked a few minutes after going on the internet! (Non Windows users can go into smug mode!)
Boot Sector Virus
The Boot Sector of a PC is a part of your computer that gets accessed first when you turn it on. It tells Windows what to do and what to load. It's like a "Things To Do" list. The Boot Sector is also known as the Master Boot Record. A boot sector virus is designed to attack this, causing your PC to refuse to start at all!
File Virus
A file virus, as its name suggests, attacks files on your computer. Also attacks entire programmes, though.
Macro Virus
These types of virus are written specifically to infect Microsoft Office documents (Word, Excel PowerPoint, etc.) A Word document can contain a Macro Virus. You usually need to open a document in an Microsoft Office application before the virus can do any harm.
Multipartite Virus
A multipartite virus is designed to infect both the boot sector and files on your computer
Polymorphic Virus
This type of virus alter their own code when they infect another computer. They do this to try and avoid detection by anti-virus programmes.
OnlineSabHow do Viruses get on my computer?
The most common way that a virus gets on your computer is by an email attachment. If you open the attachment, and your anti-virus programme doesn't detect it, then that is enough to infect your computer. Some people go so far as NOT opening attachments at all, but simply deleting the entire message as soon as it comes in. While this approach will greatly reduce your chances of becoming infected, it may offend those relatives of yours who have just sent you the latest pictures of little Johnny!You can also get viruses by downloading programmes from the internet. That great piece of freeware you spotted from an obscure site may not be so great after all. It could well be infecting your PC as the main programme is installing. And if you or your children download software from peer to peer networks (like Kazaa, Morpheus, Shareaza) then you could be downloading more than you bargained for!
If your PC is running any version of Windows, and it hasn't got all the latest patches and updates, then your computer will be attacked a few minutes after going on the internet! (Non Windows users can go into smug mode!)
OnlineSabCould I be infected by a Virus?
If you are infected by a virus, your computer may exhibit some well-known symptoms. Here's a few signs that you may be infected:- Your computer starts running more slowly than it usually does
- Your computer keep crashing
- Your computer keep crashing and then restarting
- Programmes you normally work with suddenly start behaving oddly
- You can't access your disk drives
Other symptoms to look out for are strange error messages, documents not printing correctly, and distorted menus and dialogue boxes. Try not to panic if your computer is exhibiting one or two items on the list.
The first thing to do is to scan your PC with your (up-to-date) anti virus software. If your anti-virus software fails to detect anything, then that doesn't mean you're NOT infected - it may just be poor anti-virus software. And remember, most popular doesn't mean most effective. While Norton and Mcafee are good, extensive tests in respected computer magazine show that they are not the best. Not being the best means that they may fail to detect the virus on your PC! Not only that, Norton and Mcafee are becoming really expensive to maintain!
Free Anti-Virus software
There are some good free anti-virus solutions out there. The most popular is AVG. This has gotten results that are as good as the market leaders. You can check it out here (this page also tells you what you DON'T get with the free edition):
Once installed, AVG will update itself on a regular, daily basis. It will also scan emails for viruses, and alert you if it finds anything. The interface is a bit old-fashioned but, hey, it's free and it does a quite a good job!
Another good solution is AntiVir from Avira. The classic edition is free, as well. Check out their website here:
AntiVir will also protect users of non Microsoft computers (Linux/FreeBSD/Solaris). It is, of course, debatable whether you need anti-virus protection if you don't have a Windows machine!
NOTE: If you're changing AV software, you MUST make sure that the old one has been completely uninstalled first. Norton and Mcafee can be difficult to uninstall, and you should consult their website BEFORE uninstalling - they may even have a special tool to do the job. Some people have said that trying to uninstall Norton or Mcafee was worse than getting a virus. (If you see an ad below for either of these two - it's not because we chose it!)
****************************OnlineSAB Cyber 'n' Communication*************************
