7 CLASS (21/11/2007)
2.1.4.2. E-MAIL

Electronic mail is another Internetdiensst dar. e-mail is so popular because it has a lot of advantages compared to conventional mail offers.
Email is shothand term meaning Electronic Mail. Email much the same as a letter, only that it is exchanged in a different way. Computers use the TCP/IP protocol suite to send email messages in the form of packets. The first thing you need to send and recieve emails is an email address. When you create an account with a Internet Service Provider you are usually given an email address to send from and recieve emails. If this isn't the case you can create an email address / account at web sites such as yahoo, hotmail and lycos.


The header of an email includes the From:, To:, Cc: and Subject: fields. So you enter the name and address of the recipient in the Fom: field, the name and address of anyone who is being copied to in the Cc: field, and the subject of the message obviously in the Subject: field.
The part below the header of the email is called the body, and contains the message itself.
Spelling the correct address is critical with an email. Like with a normal postal letter, if you get the address wrong it won't go the correct receiver. If you send an email to an address which doesnt exist the message will come back to you as a Address Unknown erro routine.
Email Protocols: IMAP, POP3, SMTP and HTTP
Basicaly, a protocol is about a standard method used at each end of a communication channel, in order to properly transmit information. In order to deal with your email you must use a mail client to access a mail server. The mail client and mail server can exchange information with each other using a variety of protocols.
IMAP Protocol:
IMAP (Internet Message Access Protocol) – Is a standard protocol for accessing e-mail from your local server. IMAP is a client/server protocol in which e-mail is received and held for you by your Internet server. As this requires only a small data transfer this works well even over a slow connection such as a modem. Only if you request to read a specific email message will it be downloaded from the server. You can also create and manipulate folders or mailboxes on the server, delete messages etc.
POP3 Protocol:
The POP (Post Office Protocol 3) protocol provides a simple, standardized way for users to access mailboxes and download messages to their computers.

When using the POP protocol all your eMail messages will be downloaded from the mail server to your local computer. You can choose to leave copies of your eMails on the server as well. The advantage is that once your messages are downloaded you can cut the internet connection and read your eMail at your leisure without incuring further communication costs. On the other hand you might have transferred a lot of message (including spam or viruses) in which you are not at all interested at this point.
SMTP Protocol:
The SMTP (Simple Mail Transfer Protocol) protocol is used by the Mail Transfer Agent (MTA) to deliver your eMail to the recipient's mail server. The SMTP protocol can only be used to send emails, not to receive them. Depending on your network / ISP settings, you may only be able to use the SMTP protocol under certain conditions.
HTTP Protocol:
The HTTP protocol is not a protocol dedicated for email communications, but it can be used for accessing your mailbox. Also called web based email, this protocol can be used to compose or retrieve emails from an your account. Hotmail is a good example of using HTTP as an email protocol.
The First E-mail on the Internet
In 1971, the first e-mail was typed into the Teletype terminal connected to the Digital Equipment PDP-10 in the rear of the picture below. The message was transmitted via ARPAnet, the progenitor of the Internet, to the PDP-10 in front. Dan Murphy, a Digital engineer, took this photo in the Bolt, Beranek and Newman datacenter.

2.1.4.4 FTP

The Internet is a veritable treasure trove of files and programs.
To these files on their own computers to download the File Transfer Protocol.
Practical significance is also in FTP upload their own home page on the server of the Internet provider. Students, the course IV1 visit can beispieleweise their homework exercise comfortably at home via FTP.

With the help of FTP-Protokolls it will be possible to the user files, programs, music files and the like to download. Publicly available FTP_Server can most conveniently on the browser to display. Nevertheless, the use of a separate FTP program usually practicable. If the server is open to the public talk by anonymous FTP. The user logs in as "Anonymous" on the server and used as a password in normal circumstances their own email address. In an identified FTP is entering a user name and a Passworters required. For the task of building exercises on the IDV for the login user name as the matriculation and personal password of the students.

By using its own FTP software, as shown in the above figure can be seen, the user's hard disk simultaneously directory and the directories on the server at a glance. The handling is similar to the Windows Explorer ajar, and the files can be easily using drag-and-drop up-oder Downgeloadet.

The Internet is a great treasure trove of shareware and freeware programs dar. Many manufacturers are usually for about 30 days a shareware version of their software into the network, which for this period is free testable. Freeware programs, however, are unrestricted free usage. The author maintains, however, the full copyright to the program. In addition, there is usually a number of adware programs, which are also free and unbeschränckt usable. The user must, however, with advertising displays live, he will not, he can usually an ad-free version for a fee.

Frequently there are also software, under the GPL (General Public License). GPL called Open Source Software, the user is free to use.
Additionally, the source code of the software. Interested parties may develop this software and then distribute under GPL. The mines found in software demo versions available always have a limited function scope "Commercial" always Software, which is also a demo version of the website, but their use is limited in time.

In the last few years have also exchanges like Kazaa established. The participants enter on one side files from its collection to the public free and may return the data of other users for download for their use.

The use of these exchanges is, however, great caution. Not only that many participants contaminated files to the web, in most cases users try newest MP3_Files, software and films for free to grab. This kind of exchange is, however, illegal, as it infringes the copyrights it. Program, music and video may be used only for its own budget for the purpose of backup copy burned. With the transfer to a third party makes you a criminal offense. Recent CDs and videos contain additional copy protection. This should not be cracked, a recording of an analog copy is allowed. A legal way to come to music, for example, the inclusion of a music webradio dar.

2.1.4.5. Instant Messaging/Chat

Enjoy chats on the Internet as a form of real-time communication great popularity. It can be used with people from all over the world to chat without its own identity announce it. It has been established that people in the chat room under a nickname in appearance occurs. The best known is probably the Instant Messenger ICQ. Anyone know his personal contact list, and you can see at a glance whether friends are online. In addition, of course, new contacts around the world to tap.

Apart from the traditional chat, it is with Instant Messaging Conference talks to lead or online to play. Even in the division Instant messaging is gaining in importance.

2.1.5.1. Safety in internet

2.1.5.1. VIRUSES

Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation.
A virus might corrupt or delete data on your computer, use your e-mail program to spread itself to other computers, or even erase everything on your hard disk.
Viruses are most easily spread by attachments in e-mail messages or instant messaging messages. That is why it is essential that you never open e-mail attachments unless you know who it's from and you are expecting it.
Viruses can be disguised as attachments of funny images, greeting cards, or audio and video files.
Viruses also spread through downloads on the Internet. They can be hidden in illicit software or other files or programs you might download.
To help avoid viruses, it's essential that you keep your computer current with the latest updates and antivirus tools, stay informed about recent threats, and that you follow a few basic rules when you surf the Internet, download files, and open attachments.
Once a virus is on your computer, its type or the method it used to get there is not as important as removing it and preventing further infection.
TROJANS
In computers, a Trojan horse is a program in which malicious or harmful code is contained inside apparently harmless programming or data in such a way that it can get control and do its chosen form of damage, such as ruining the file allocation table on your hard disk. In one celebrated case, a Trojan horse was a program that was supposed to find and destroy computer viruses. A Trojan horse may be widely redistributed as part of a computer virus.
HOAXES
The Hoaxs (joke or deceit), they are messages with false alarms of virus, or of any other type of alert or chain (even shared in common, or that involves our own health), or of some type of denunciation, distributed by electronic mail, its common denominator, it is to request to him distributes them "to the greater possible amount of well-known".
These alarms, usually they are TOTALLY FALSE, or based on erroneous facts, but what is worse they activate a type of "contamination" very different, propagate hundreds and up to thousands of warning messages on such. And still in the case of denunciations based on fact real, this form to do weakens it totally its true objective.
This is a description of hoaxes more common that they circulate around the network. It never returns to send no of these messages. If somebody of good faith sends one to him of these alarms, avi him to it of pages like this so that it leaves its deceit and it obtains more.

2.1.5.2. FIREWALL

A firewall is a set of related programs, located at a network gateway server, that protects the resources of a private network from users from other networks. (The term also implies the security policy that is used with the programs.) An enterprise with an intranet that allows its workers access to the wider Internet installs a firewall to prevent outsiders from accessing its own private data resources and for controlling what outside resources its own users have access to.
Basically, a firewall, working closely with a router program, examines each network packet to determine whether to forward it toward its destination. A firewall also includes or works with a proxy server that makes network requests on behalf of workstation users. A firewall is often installed in a specially designated computer separate from the rest of the network so that no incoming request can get directly at private network resources.
There are a number of firewall screening methods. A simple one is to screen requests to make sure they come from acceptable (previously identified) domain name and Internet Protocol addresses. For mobile users, firewalls allow remote access in to the private network by the use of secure logon procedures and authentication certificates.
A number of companies make firewall products. Features include logging and reporting, automatic alarms at given thresholds of attack, and a graphical user interface for controlling the firewall.
Computer security borrows this term from firefighting, where it originated. In firefighting, a firewall is a barrier established to prevent the spread of fire

2.2 Search and Find on the Internet

Often, the term is inaccurate search engines for all types of search tools. In this issue very soon, many well-known throughout the Google search engine and all too easy to forget that there are a lot of good search tools and search strategies, especially for the efficient search on the Internet note.


2.2.1. Search


A search engine is a service on the Internet, with the parts you can browse the Internet. A search engine can be equipped with a Indez or a keyword index in a book compared.

For the user is presented a search engine on the Web site, like any other web page. In one form of search criteria can be entered.
In addition, the search to specific objects, bestimmnte addresses or to a specific date range may be restricted.

The search engine provides the user a list of Web Addresses, the criteria at its best.

On the Internet, there are numerous search engines.
Some try to cover the whole WWW, others seek only in a certain part of the WWW pages only in the German language.
But not all websites can be searched via search engines.

How does a search engine?

A search engine searches the Internet when the user submits a search query. Among the billions of documents on the Internet would be much too long. A search engine consists of three parts robots, Indez and Benutzer-Schnitstelle: Very simply, it will be declared websearch.about.com


The technical development of a search engine is demostrate on a schematic representation in the book, but I couldnt copy it here, and with it you can understand the technical development of a search.