Bits of the Internet
DNS (Domain Name Servers)
A URL (Uniform Resource Locator) such as http://www.mckinnonsc.vic.edu.au or an email address like fred@somewhere.com is easy for a human to remember and understand, but it's no good for computers. They work best with numbers.
All sites on the Internet are actually referred to by number, called an IP address. It usually consists of 4 'octets' of numbers e.g. 10.77.91.19 or 209.112.113.56 where each number between the dots can be from 0 to 255.
In fact, you could type in the IP address of a site into a browser instead of a URL and it would find the site. Actually it would be faster than using a URL because the browser would not need to look up the IP address on a DNS server.
Some
details of how you can find out IP addresses
When you enter a URL, it has to be translated into an IP address before you can go anywhere: this is what the DNS (Domain Name Servers) do. The Domain Name system is a distributed database containing information on every internet location on the planet. It is forever changing as new sites appear, move or disappear.
The DNS is like a massive phone book. To visit a site, your browsers looks up the domain name in the DNS "phone book" and reads across to get its IP address ('phone number') and that's actually what the browser uses to contact the site.
Some IP addresses are dynamic: they are assigned to computers for the duration of one internet session, and are then released and reused by someone else. When you connect to an ISP by dialup modem, your ISP assigns you an IP address for the duration of your connection from a pool of IP addresses that has been allocated to that ISP. (This means you get a different IP address every time you connect to the Internet. It suits your ISP because they just need enough IP addresses to cover the number of modems they have, rather than an IP address for each customer.)
When you turn on a college computer, it requests an IP address from the file server: the server uses its DHCP service to find an unused IP address from the pool of IP addresses it has been allocated by the college's ISP. The size of the college's (or other organisation's) IP address pool depends on how many people it needs to allow online at the same time (and how much they can afford!)
Other IP addresses are static: that is, they are assigned to a computer and that computer keeps a hold of that IP address more-or-less permanently. File servers, internet servers, websites and computers with cable modems usually have static IP addresses because they need to be locatable over periods of time.
For the name of a site to be associated with an IP address, the domain name must be registered. There are many registrars who manage this. By registering a domain name, you stop anyone else using it for a period (e.g. 1 year). If you fail to renew it when it expires, someone else can jump in and claim it.
All you then have to do is give the registrar the IP address that will be associated with the domain so DNS servers can find the domain by name.
While it is important to have a central authority keeping track of the database of names in the COM (and other) top-level domains, there are thousands of distributed domain name servers around the world managing their own domains. For example, Microsoft has hundreds of thousands of IP addresses and host names and they maintain their own domain name server for the microsoft.com domain. Similarly, Great Britain administrates the uk top-level domain, and Australia administrates the au domain, and so on. For this reason, the DNS system is a distributed database. Microsoft is completely responsible for dealing with the name server for microsoft.com -- it maintains the machines that implement its part of the DNS system, and Microsoft can change the database for its domain whenever it wants to because Microsoft owns its domain name servers.
Every domain has a domain name server somewhere that handles its requests.
The DNS system's database is distributed throughout the world on millions
of machines administered by millions of people, yet it behaves like a
single, integrated database!
When you enter a URL into your browser, your ISP's domain name server looks up the name in its own database. If it finds it, it returns the IP address and off you go to that site. If your ISP's DNS cannot "resolve" the name, it passes it along to a bigger DNS somewhere else in the world. If that DNS can't identify the name, it passes it to yet another DNS. After about 4 attempts, if the name is not found, an error message is returned.
FTP (File Transfer Protocol)
FTP is used to send files across the Internet. It is often used to distribute
software. One of the most common uses of FTP is to upload (send) pages
to your website. Common FTP programs are CuteFTP, WS-FTP. Many big web
page editors and even file managers have FTP abilities built in.
An FTP program looks a lot like a standard file manager, but it has two "panes": one is your local hard disk and the other pane shows the contents of the remote computer. File transfer is as easy as dragging files from one pane to the other.
CuteFTP in action
WWW
The World Wide Web deals mainly with websites and web pages written using HTML (Hypertext Markup Language). It uses the Hypertext Transfer Protocol (HTTP) to transfer web page files.
TCP/IP
TCP/IP is actually a matching pair of communication protocols that manage most Internet and network traffic. The TCP protocol handles the job of breaking files into packets for transmission and reassembling packets into files after they are received. The IP protocol is in charge of getting packets from one place on the internet to another.
Electronic mail has become one of the "killer applications" of the Internet: it is one of the main reasons some people get onto the Internet in the first place. A simple text editor lets you compose mail, and it is sent over the internet to its recipient(s) as a normal file transfer. There are more advanced email software features that let you:
- create mailing lists (so you can send an email to many people at once)
- store email addresses so you don't have to type them in every time
- filter incoming email, e.g. to sort different messages into different folders or delete unwanted email
- attach files to email
An email address has the form of - username@domain (e.g. fred@isp.com)
Tip: to insert a clickable email link into a webpage, the HTML you need is:
mailto:fred@isp.com
You can get fancier and fill in some of the email's fields. To specify the subject of the email, do this:
mailto:fred@isp.com?subject=This is the subject of the email
You can fill in other fields too...
mailto:fred@isp.com?subject=This is the subject of the email&body=This is the body
Spam (or UCE - unsolicited commercial email) is the modern curse of Internet users. Email becomes spam if it is unsolicited [you didn't ask for it] or if it is sent to many recipients. Spammers are often mass-marketers who can send a million emails a day and hope that 1% of recipients read them, and are overjoyed if 0.01% actually show interest. They buy the email address lists from address harvesters who grab email addresses from websites, Usenet and companies who sell their customers' email addresses.
Tip: It has often been recommended that you never use the "Click here to remove yourself from this mailing list" link because it would signal the spammer that you were a live email address. Recent research, however, tends to suggest that this does not happen. It is more likely that the "unsubscribe" email address is a fake anyway and it does no good to click it. Reputable organisations, however, will honour unsubscription requests (but they rarely spam people anyway.)
It is easy to become annoyed at spammers and want to seek revenge. Alas, spammers know you hate them, and take elaborate precautions to avoid detection. If you read the hidden "headers" of a spam email, you often find it is impossible to trace where the spam really came from. Even if you manage to track them down, and their ISP is willing to take action against them, it often does you no good. They would re-surface the next day with a different email account or ISP and continue business as normal. Sigh :-(
It is definitely unwise to attempt retaliation with such tactics as "mailbombing" - using software to send multiple mail to the spammer's address. If your ISP caught you doing it, you would likely lose your Internet account.
USENET
Usenet is made up of newsgroups where millions of people discuss issues of joint interest. There are tens of thousands of newsgroups, and if you have an interest, there is guaranteed to be at least one newsgroup you could subscribe to.
Which newsgroups you have access to depends on which groups your ISP wants to 'feed': few ISPs would carry every newsgroup in the world (fetching all the messages involves a massive amount of downloading). Sending a 'post' to a newsgroup is nearly identical to sending an email (in fact in Netscape, newsgroups are a part of email). The only difference is that instead of the message going to a single person, it goes to the newsgroup for the world to see.
Hint: Always think carefully before sending a message to a newsgroup. Once sent, the message will be visible across the world, and once sent, it's nearly impossible to cancel it!
If you want to investigate newsgroups without setting anything up on
your computer, you can use Google
Groups.
Beware: Usenet
is largely an unmoderated adult forum - there are many unpleasant topics
and fruity language to be found there!
A
Usenet post dissected and explained
How
to create a new newsgroup in the ALT.* hierarchy
Search Engines
Details on search engines are here
Firewalls
A firewall is a software or hardware device (a router) to protect your computer against hackers. It watches the thousands of communication ports your internet connection has, and alerts you if unauthorised traffic is seen where it should not happen.
Good firewalls watch not only for dangerous incoming messages, but also watch for unauthorised outgoing messages, such as those from Trojan Horses that have found their way onto your system.
Zone Alarm is an excellent and free firewall: when any program on your system tries to access the Internet for the first time, Zone Alarm asks you whether you want the progrma to do this. You can say "Yes, just this once", "Yes, any time" or "No, not any time". It lets you control who invades your system, and who your system talks to. Some firewalls only check incoming communications: Zone Alarm is one of the few that also monitors outgoing communcations.
Microsoft now packages a basic firewall with Windows XP. It's better than nothing.
If you have a cable connection to the Internet you probably have a static IP address, and a firewall is virtually compulsory. If, however, you use a dial-up modem connection to your ISP, you will get a differerent IP address every time you connect, so it is harder for hackers to determine your location. Even on a dial-up connection, however, it is alarming how soon you will find someone trying to do a "port probe" to see if your computer is vulnerable.
Want
to see how the functions of your 65,536 internet ports
are assigned?
SPYWARE
Spyware is software that monitors your internet activity, and often reports it to companies that distribute advertising. Spyware is often installed stealthily. For example, when you install Kazaa, buried deep in the EULA (End User Licence Agreement) that you must accept before installing, is this... (interesting bits have been bolded by me)
9.4 Embedded Third Party Software
9.4.1 Cydoor. The Software includes a Cydoor Technologies advertising delivery program, which may display web content such as banner ads, e- commerce offers, news headlines and other value-added content. The Cydoor component uses your Internet connection to update its selection of available ads and stores them on your hard drive. For information on Cydoor Technologies and their software, go to http://www.cydoor.com. For information on their privacy policy, go to http://www.cydoor.com/Cydoor/Company/CompanyPrivacy.htm.
9.4.2 Topsearch. The Software includes the Topseach software provided by Altnet. The Topsearch component regularly downloads an index of available Altnet content through your Internet connection. This index contains a list of available rights managed files which can be displayed in your search results. For information on Altnet and their software, go to http://www.altnet.com. For information on their privacy policy, go to http://www.altnet.com/privacy/.
9.4.4 GAIN AdServer. Kazaa Media Desktop incorporates a software component called the GAIN AdServer, which is provided by GAIN Publishing. The GAIN AdServer software identifies your interests based on some of your computer usage and uses that information to deliver advertising messages to you. This software helps keep Kazaa Media Desktop free. The GAIN AdServer is provided pursuant to the GAIN Publishing End User License Agreement and Privacy Statement (located at http://www.gainpublishing.com/help/psdocs/kmd/privacy-help51.html), which you acknowledge that you have read and accept. If you would like to stop receiving advertisements through the GAIN AdServer, you will need to remove all GAIN supported software from your computer, including Kazaa Media Desktop, using the Add/Remove Programs Control Panel. For further information on GAIN Publishing and the GAIN AdServer, go to http://www.gainpublishing.com/.
9.4.5 PerfectNav. Kazaa Media Desktop comes with a software program called PerfectNav, which is provided by eUniverse, Inc. PerfectNav is designed to redirect your URL typing errors to PerfectNav's web page. This software helps keep Kazaa Media Desktop free. The PerfectNav software is provided pursuant to the PerfectNav End User License Agreement (located below as Exhibit A), which you acknowledge that you have read and accept. For further information on eUniverse, go to http://www.euniverse.com/.
9.4.6 In exchange for downloading the Software at no cost, you expressly agree that you accept the Embedded Third Party Software and that you will not take any action, including downloading other software intended to, or modifying or permitting others to modify registry or other settings on your computer to, disable or remove the Embedded Third Party Software or to prevent its functioning.
It is hard to know exactly what spyware may be doing in your system, and often spyware is badly programmed and causes system malfunctions or just chews up processor time and memory. You can search for and remove Spyware by using AdAware (even if KaZaA expressly forbids you to do that!)