by Dean Moor

This month we are privileged to be able to include the second in a series of articles by one of our customers, Dean Moor.  Dean has a long-standing interest in computer security and has graciously agreed to share some of his knowledge.

Always remember - one of the best ways to protect your security online is to change your password on a regular basis. Haven't done that for a while? Do it now. Call our help desk (0800-228749) if you're not sure how. -Ed.

Before I go too far ahead I need to ensure you have a basic knowledge of how the Internet works. I find the analogy of a city is the best to use. A city is made up of thousands of houses, connected to each other by roads. The Internet, in comparison, is made up of thousands of computers, connected by modems. Now, every house in a city has an address, which may look like this:

15 Somewhere St.
Atawhai
Nelson

On the Internet, every computer has an address, similar to that of a house somewhere in a city, the only difference is the way that address looks. An Internet Address consists of 4 numbers separated by a "." such as, 203.96.28.15

Notice how the last number in the Internet Address is the equivalent of the house number, the second to last is the street, and so on. You may be wondering what the significance of this is. You shall see shortly.

Now that we have a basic understanding of the address scheme the Internet uses, lets look at one more thing you need to be aware of - Ports. I am sure most of you may have heard about ports, yet don't completely understand them. Most of my customers seem to think they are the things on the back of your machine box where your mouse, keyboard and various other peripherals are plugged in. This is true, but when talking about the Internet, ports are something completely different.

Let us take the analogy that we used before with the city.

Your Internet connected computer could now be referred to as your house. Now, almost all houses have doors and windows. There is a front door, back door, sometimes a door through to the garage, and so forth. Each room has windows that are most likely referred to by style or size. Well, now lets call these doors and windows, ports. Just as we have a way of describing the doors and windows there is a method of describing ports, and as with almost all computing related names, it a numerical method. For example, almost every one comes in through the front door so we shall refer to this as the port that the web pages come in on. This is port 80. Now, emails come in through the large opening windows in the lounge (Port 110) and out through the small window in the dining room (Port 25). Please remember that this is a very simple model.

To sum it all up, I would say ports are the entry/exit points to our computer that its programs use to interact with other computers. Certain types of program use certain ports, while others use other ports.

Ok, now to answer the question of how does someone find me? From my own experience, the majority of "Hackers" are not looking particularly for you. They are usually opportunistic, just after anyone online that they can "Hack." One way they find a computer is to run a domain scanner. You may be wondering what a domain scanner is? Well, lets go back to our city analogy. A domain in the city model would be the suburb in a city. For example, Atawhai, Nelson. If we were to place this in the Internet address scheme, we would end up with,

Nelson = 204.
Atawhai=96.

Therefore, the IP (Internet Protocol) address for Atawhai, Nelson would be 204.96.

Notice how the Internet seems to have the address back to front? Well this is because a computer generally processes things in a logical order, where as we humans process information completely back to front!