The main information resources of the Internet. Basic Internet resources What is working with Internet resources

Internet resources.

Internet - a global computer network created quite a long time ago and developed as a departmental network owned by the US Department of Defense. However, it quickly became available to ordinary users, and starting from 1990, when the number of its users began to grow sharply, and, especially, from 1993, when the WWW system was invented ( English World Wide Web), the Internet has become a completely different kind of phenomenon. Internet- this is a huge amount of information available from any computer connected to the network, this is a new means of communication and mass media, which differs from the usual openness, accessibility and democracy.

At the core of the Internet is "client" system – server" . The information on the web is located on a huge variety of servers scattered around the world. To communicate with them and view the information received from there, special client programs are installed on the computers of network users ( browsers ) .

To distinguish computers on the Internet, each of them is assigned an address, which is a unique string of numbers or a symbolic computer name corresponding to this string.

When sending information by TCP / IP protocols, the digital (IP address) of the computer is used, which is four decimal numbers separated by a dot, for example, 172.20.0.250.

An IP address is a four-byte binary number represented as four decimal numbers separated by a dot that uniquely identifies a computer connected to the Internet.

There is a special organization on the Internet that checks and issues addresses.

For convenience, a digital address can be represented as a string of characters. This means that the computer has a name or a domain address. Each part of a domain name is called a domain. The number of domains can be different, but most often there are three to five. The domain name is read from right to left and is decoded as a sequential specification of the address, similar to the postal address system.

Servers are owned, as a rule, by large companies, news agencies, authorities, interest clubs, educational institutions, etc. Each Internet server has its own electronic address. These addresses are called domain (Fig. 1), because they consist of names domains (English . Domainarea, region) - a set of computers to which this computer belongs. Domain names consist of segments written from right to left and separated by dots, i.e. the computer name is on the left, the name of the top-level domain corresponding to the country or, less commonly, to any large group of servers, is on the right.

For example: the domain name ru means Russia, ua - Ukraine, au - Australia, edu - educational institutions, com - commercial organizations (Fig. 1). It is clear that there is no computer on the Internet that would know the addresses of all other computers on the network and how to connect to them. This is impossible, just as the existence of a worldwide telephone book is impossible.

However, there are special DNS servers (English . Domain Name Service, distributed around the world, each of which is responsible for some part of the network. When it needs to find some other computer connected to the Internet, the computer contacts one DNS server. If the address required by the user is not found on this DNS server, the latter will “turn” to other DNS servers, those to the next, and so on. Thus, a user’s request can fly around the world in a matter of seconds.

Rice. 1. An example of a domain address

Used to search for information on the web resource address (English . Uniformresourcelocator (URL) the address), containing the name of the protocol by which you need to access the required information, the server address and the file name on this server (Fig. 2).

Rice. 2. An example of a resource address

Filenames on integrated servers tend to look odd. This is due to the fact that servers most often run under the UNIX operating system, in which the rules for writing file names are different from those accepted in Windows.

The file name may be missing. In this case, the network user will be sent from the server a file pre-installed for this case (“by default”).

Organization of information exchange on the Internet

Client-server interaction occurs according to certain rules, or, as they say differently, according to the protocol. In terms of protocols, the Internet uses several types of protocols that have evolved over time and are associated with the development of computer technology.

When exchanging data on the Internet, it is necessary to provide a connection between the client and the server. But knowing only the IP address of the computer is still not enough, because. Ultimately, it is not the computers themselves that exchange information, but the applications that run on them. And several applications can run simultaneously on a computer (for example, a mail server, a web server, etc.).

To deliver an ordinary paper letter, it is not enough to know only the address of the house - you also need to know the number of the apartment. Also, every software application has a similar number, called a port number. Most server applications have standard numbers, for example: the mail service is bound to port number 25 (they also say: it “listens” on the port, receives messages on it), the web service is bound to port 80, FTP is bound to port 21, and so on.

The Internet uses a family of protocols TCP/ IP (transmissioncontrolProtocol/ InternetProtocol, Transmission Control Protocol/Internet Protocol)- which is a standard for transferring data between networks, including the Internet.

Protocol TCP (Transmission Control Protocol) breaks information into portions (packets) and numbers them. Then protocol IP (Internet Protocol) adds service information to each portion with the addresses of the sender and recipient and ensures the delivery of all packets.

Thanks to this method of transmitting information, on the Internet, as in regular mail, there is no concept of "busy" - each computer can simultaneously receive packets from a large number of other computers. In this case, there is no need to establish a separate communication channel between the two computers.

Each Internet resource has its own protocol. Internet resource protocols are called application protocols, they all use TCP/IP as the transport layer protocol.

These include the telnet text protocol, the ftp file protocol, the Usenet teleconferencing protocol, the wais database protocol, the gopher protocol, and others.

TCP/IP is the name of the network protocol suite. In fact, the transmitted packet goes through several levels. (Like in the mail: first you write a letter, then you put it in an envelope with an address, then a stamp is put on it in the mail, etc.).

IP A protocol is a so-called network layer protocol. The task of this layer is to deliver IP packets from the sender's computer to the recipient's computer. In addition to the data itself, packets of this level have a source IP address and a destination IP address. Port numbers are not used at the network level. Which port, i.e. this packet is addressed to the application, whether this packet was delivered or was lost, it is not known at this level - this is not its task, this is the task of the transport layer.

TCP and UDP These are the protocols of the so-called transport layer. The transport layer sits above the network layer. This level adds a source port and a destination port to the packet.

TCP is a connection-oriented protocol with guaranteed delivery of packets. TCP (transmission control protocol) breaks information into chunks (packets) and numbers them. Then the IP protocol (Internet protocol) adds service information with the sender and recipient addresses to each portion and ensures the delivery of all packets.

You can interpret the work of TCP as follows. First, special packets are exchanged to establish a connection, something like a handshake takes place (Hi. -Hi. -Let's chat? -Come on.). Further, packets are sent back and forth over this connection (there is a conversation), and with a check whether the packet has reached the recipient. If the packet did not reach, then it is sent again (“repeat, did not hear”).

UDP is a connectionless protocol with non-guaranteed packet delivery. (Like: shouted something, but whether they hear you or not - it doesn’t matter).

Above the transport layer is the application layer. Protocols such as HTTP and FTP, etc. work at this level. For example, HTTP and FTP use the reliable TCP protocol, while the DNS server works through the unreliable UDP protocol.

Thanks to this method of transmitting information, on the Internet, as in regular mail, there is no concept of "busy" - each computer can simultaneously receive packets from a large number of other computers.

In this case, there is no need to establish a separate communication channel between the two computers.

The protocol adopted by the WWW is called the HyperText Transfer Protocol, or HTTP for short. An indication of it in the resource address is the designation http ( English. Hyper Text Transfer Protocol (hypertext transfer protocol). HTTP (HyperText Transfer Protocol) is the protocol that a Web client uses to retrieve a Web page from a Web server.

This protocol for transmitting hypertext on the Web was proposed by the Swiss physicist Tim Berners-Lee in 1989.

Basic resources (services) of the Internet

The most popular Internet resource is the World Wide Web or WWW, which is a huge number (over a billion) of multimedia documents, the distinguishing feature of which, in addition to their beautiful appearance, is the ability to link to each other. This means the presence in the current document of a link that implements the transition to any WWW document that can be physically located on another computer on the Internet. WWW (World Wide Web) is a collection of interconnected hypermedia documents.

The next network resource is FTP, which is a storage and transfer system for all kinds of files. FTP (File Transfer Protocol) is a storage and transfer system for all kinds of files.

The oldest Internet resource is E-mail (electronic mail). E-mail (electronic mail) - a system for sending emails. There is even a special, cheaper mail connection to the Internet that provides connection only to e-mail.

To conduct discussions on the network, a global distributed system called Newsgroups is designed. Newsgroups is a global distributed system for messaging and discussion. One of the most popular systems of this kind are the Usenet newsgroups.

The telnet service allows you to connect to a remote computer and access its resources. Telnet is a service for remote control of computers. Most often, however, these computers are running some variant of the Unix operating system (Unix), so this service is currently used primarily by system administrators.

Finally, the Internet has an IRC (Chat) system that implements live communication between users in real time by entering text from the keyboard. IRC (Chat) is a service for live communication of Internet users in real time by entering text from the keyboard.

When connecting a local network to a global network, data security becomes important. To ensure network security between the local and global networks, a special computer or program (firewall) is installed that restricts access to the local network from the outside and unauthorized access outside the local network.

The Internet has the following modes of operation:

Online– mode of operation, which means direct connection to the network for the entire time of requesting, searching, processing, receiving and viewing information.

Most Internet services, such as WWW, operate in this mode.

off-line– mode of operation, implying connection to the network only for the time of sending a request or receiving information on request mode of operation. In this mode, for example, e-mail works.

In the modern sense, an Internet resource is a collection of electronic documents or files united by one IP address or domain. All Internet sites (or Internet resources, which is equivalent) are located on servers remote from each other, the combination of which is called the World Wide Web. It is she who combines various pieces of information from the network into a single whole.

Varieties of Internet resources

The second criterion by which sites are divided on the network is its location. It can be accessed from the Internet, when absolutely any user can get to this resource, or in the local network. In this case, the availability of the site is limited to a certain range of IP addresses.

The most difficult criterion by which Internet sites are divided is the scheme for dividing the provision of information to the user. There are so-called Internet portals that have a complex hierarchy, consisting of many pages and including a lot of data. The portal may consist of many interdependent sites united by a single theme, etc. There are also information resources, most often they are devoted to a specific topic.

Internet representations and web services deserve special attention. The purpose of the former is to provide information to users about any business, company, project, etc. Web services are created to perform certain tasks within the current technical development of the Internet (hosting, search, bulletin boards, mail services, forums, etc.)

Khabarovsk

INTRODUCTION.. 4

2. Theoretical part. 5

2.1 Finding information. 5

2.2 Internet services and resources. 6

2.3 Web service. 12

2.4 Network security. 14

2.5 Firewalls. 15

2.6 Protection of the site from viruses and hacking. 17

2.7 Website. 20

2.8 Ways to create sites. 22

2.9 Stages of site creation. 23

2.10 Hosting. 24

2.11 Installing a web server on a local computer. 25

2.12 CMS installation. 25

2.13 HTML hypertext markup language. 26

2.14 Website design. 27

2.15 Site structure. 28

2.16 Ways of placing the site on the Internet. 29

3. Site Administrator Guide. 30

CONCLUSION.. 33

LIST OF SOURCES.. 34

INTRODUCTION

The purpose of the internship is the implementation of the theoretical knowledge, skills and abilities, as well as getting an idea about the practical activities of the organization. To achieve the goals set during the internship, the following tasks were set:

Acquaintance with the working conditions of the enterprise and with your workplace, namely with the internal regulations, safety requirements, physiological and hygienic basics of the labor process and sanitation requirements;

The study of normative and methodological materials, fundamental and periodic literature in accordance with an individual task;

Use of information and communication technologies;

Fulfillment of an individual task;

Preparation of practice report.

Practice goals:

Expansion, deepening and systematization of knowledge gained in the process of theoretical training;

Consolidation of practical skills in the development and technical support of websites;

Formation of general and professional competencies.

Theoretical part

Search for information

Ways to find information on the web

Searching for information is one of the most popular tasks in practice that any Internet user has to solve.

There are three main ways to find information on the Internet:

1. Indication of the page address.

3. Access to the search engine (search server).

Method 1: Specifying the page address

This is the fastest way to search, but it can only be used if you know exactly the address of the document or the site where the document is located.

Do not forget the ability to search on a web page open in a browser window (Edit-Find on this page ...).

This is the least convenient method, since it can be used to search for documents that are only similar in meaning to the current document.

Method 3: Contacting a search engine

to travel in the information space of the Web, moving from one web page to another, but given that many millions of web pages have been created in the world, it is unlikely that you will be able to find the necessary information on them in this way.

Special search engines come to the rescue (they are also called search engines). Search server addresses are well known to everyone who works on the Internet. Currently, the following search engines are popular in the Russian-speaking part of the Internet: Yandex (yandex.ru), Google (google.ru) and Rambler (rambler.ru)

Search system

Search engine - a website that provides the ability to search for information on the Internet.

Most search engines look for information on World Wide Web sites, but there are also systems that can look for files on ftp servers, items in online stores, and information on Usenet newsgroups.

According to the principle of operation, search engines are divided into two types: search directories and search indexes.

Search directories

Search directories serve for thematic search.

The information on these servers is structured by topics and subtopics. With the intention of covering a narrow topic, it is not difficult to find a list of web pages devoted to it.

A catalog of resources on the Internet or a catalog of Internet resources, or simply an Internet catalog - a structured set of links to sites with a brief description of them.

Search indexes

Search indexes work like alphabetical indexes. The client specifies a word or a group of words that characterize his search area - and receives a list of links to web pages containing the specified terms.

The first search engine for the World Wide Web was Wandex, a now-defunct index developed by Matthew Gray of the Massachusetts Institute of Technology in 1993.

How does a search index work?

Search indexes automatically, with the help of special programs (web spiders), scan Internet pages and index them, that is, they enter them into their huge database.

A search robot (“web spider”) is a program that is an integral part of a search engine and is designed to crawl Internet pages in order to enter information about them (keywords) into the search engine database. At its core, the spider most closely resembles a regular browser. It scans the content of the page, uploads it to the server of the search engine that owns it, and sends it through links to the following pages.

In response to a query where to find the required information, the search server returns a list of hyperlinks leading to web pages that contain or mention the required information. The length of the list can be any, depending on the content of the request.

Internet Services and Resources

The Internet is a global computer network that includes millions of servers and client computers, consists of various communication channels and works thanks to certain technologies. Thanks to all of the above, it became possible to transfer information from one computer to another, but what kind of information, more precisely, what type, format? How will this information be presented on the user's computer? What rules and scenarios for working with this information will be used? The answers to these questions are provided by descriptions of the services (services) that operate on the Internet.

Services (services) are the types of services that are provided by the servers of the Internet.

In the history of the Internet, there have been different types of services, some of which are no longer in use, others are gradually losing their popularity, while others are flourishing.

We list those of the services that have not lost their relevance at the moment:

World Wide Web - the World Wide Web - a service for searching and viewing hypertext documents, including graphics, sound and video.

E-mail - electronic mail - an electronic message transmission service.

Usenet, News - teleconferences, newsgroups - a kind of online newspaper or bulletin board.

FTP is a file transfer service.

ICQ is a service for real-time communication using the keyboard.

Telnet is a service for remote access to computers.

Gopher is an information access service using hierarchical directories.

Among these services, we can distinguish services designed for communication, that is, for communication, information transfer (E-mail, ICQ), as well as services whose purpose is to store information and provide users with access to this information.

Among the latter services, the leading place in terms of the amount of stored information is occupied by the WWW service, since this service is the most convenient for users to work with and the most progressive in technical terms. In second place is the FTP service, because no matter what interfaces and conveniences are developed for the user, information is still stored in files, access to which this service provides. Gopher and Telnet services can now be considered “dying off”, since new information is almost no longer received by the servers of these services, and the number of such servers and their audience is practically not increasing.

Internet content structure

World Wide Web - world wide web

The World Wide Web (WWW) is a hypertext, or rather, hypermedia information system for searching for Internet resources and accessing them.

Hypertext is an information structure that allows you to establish semantic links between text elements on a computer screen in such a way that you can easily navigate from one element to another.

In practice, in hypertext, some words are highlighted by underlining or coloring in a different color. Highlighting a word indicates the presence of a connection of this word with some document in which the topic associated with the highlighted word is considered in more detail.

Hypermedia is what happens if in the definition of hypertext we replace the word "text" with "any kind of information": sound, graphics, video.

Such hypermedia links are possible because, along with textual information, any other binary information, such as encoded sound or graphics, can be linked, so if the program displays a map of the world and if the user selects a continent on this map with the mouse, the program can immediately give graphic, sound and text information about it.

The WWW system is built on a special data transfer protocol called the HyperText Transfer Protocol (HTTP).

All contents of the WWW system consist of WWW pages.

WWW pages are hypermedia documents of the World Wide Web system. They are created using the Hypertext Markup Language (HTML).

A set of Web pages linked together by links and designed to achieve a common goal is called a Web site.

Email.

E-mail appeared about 30 years ago. Today it is the most massive means of information exchange on the Internet.

E-mail (Electronic mail, English mail - mail, abbr. e-mail) is used to send text messages within the Internet, as well as between other email networks.

Using e-mail, you can send messages, receive them in your electronic mailbox, reply to letters from correspondents, send copies of letters to several recipients at once, forward the received letter to another address, use logical names instead of addresses, create several mailbox subsections for various kinds of correspondence, include in letters various sound and graphic files, as well as binary files - programs.

A computer connected to the network is considered a potential sender and receiver of packets. Each Internet node, when sending a message to another node, breaks it into packets of a fixed length, usually 1500 bytes. Each packet is supplied with a destination address and a sender address. Packets prepared in this way are sent via communication channels to other nodes.

Upon receipt of any packet, the node analyzes the recipient's address and, if it matches its own address, the packet is accepted, otherwise it is sent further. Received packets related to the same message are accumulated. Once all packets of a single message have been received, they are concatenated and delivered to the recipient. Copies of packets are stored on the sending nodes until a response is received from the receiving node about the successful delivery of the message. This ensures reliability. To deliver a letter to the addressee, you only need to know his address and the coordinates of the nearest mailbox. On the way to the addressee, the letter passes through several post offices (nodes).

The process of step-by-step determining the path of a letter is called routing.

When using e-mail, each subscriber is assigned a unique postal address, the format of which is as follows:

<имя пользователя> @ <имя почтового сервера>.

For example, [email protected], where earth is the username, space.com is the computer's name, @ is the delimiter "at commercial", often referred to as "dog".

E-mail does not require the simultaneous presence of both subscribers at different ends of the line. Messages received by e-mail are stored in a special "mail" computer in an area of ​​disk memory allocated for the recipient (his "mail box"), from where he can upload them and read them using a special client program. To send a message, you need to know the email address of the subscriber. With high-quality communication, an e-mail reaches anywhere in the world within a few minutes.

When sending mail, the program communicates with the outgoing mail server, or SMTP server, using the SMTP (Simple Mail Transfer Protocol) protocol.

When receiving mail, the program contacts the incoming mail server or POP3 server using the POP3 (Post Office Protocol 3) protocol. It can be both different computers, and the same one. Server names are provided to users by the provider.

The more modern IMAP protocol allows, in particular, to selectively copy received letters from the mail server to the computer. To use this protocol, it must be supported by both the provider and the mail program.

FTP file transfer service.

As you know, all information is stored in files. The file can have a different size and contain absolutely any information. That is why a huge number of various files have accumulated on the Internet over the past 15-20 years, the archives of which are accessed using the FTP file transfer service.

The FTP file transfer service moves copies of files from one Internet site to another using the FTP (File Transfer Protocol) protocol.

It does not matter where these nodes are located and how they are interconnected.

Computers that have shared files are called FTP servers.

FTP itself and ftp access tools predated Web browsers and HTML. And this is not surprising, since the transfer of binary data from computer to computer has always been the main task of the Internet.

There are over 10 Terabytes of free files and programs on the Internet. Any user can use the services of the FTP service and use anonymous access to copy the files of interest to him.

In addition to programs, FTP archives contain Internet standards, press releases, books on various fields of knowledge (and especially on computer issues), and much more.

For the user to work with the FTP service, there are many FTP client programs, for example, CuteFTP, Far, Windows Commander. As a rule, these programs are also file managers, that is, they allow you to view both information on local drives, and exactly the same on remote ones, and perform the functions of copying information from a remote drive to a local drive.

Access to files on file archive servers is possible both via HTTP and FTP protocols. The FTP protocol allows not only downloading files from remote file archive servers to the local computer, but, conversely, transferring files from the local computer to a remote Web server, for example, in the process of publishing a Web site.

Usenet teleconferencing system.

A very similar service to email is the Usenet newsgroup.

News is one of the oldest means of communication in the history of the Internet between groups of people interested in one specific issue. Usenet news (from the English user "s network, user network) was invented by three American students in 1979. Usenet served at that time to distribute information and news on programming. The data was sorted into fifteen headings, which later became known as "news groups", " conferences or teleconferences.

The Usenet newsgroup organizes group discussions on

various directions, called teleconferencing. This service uses the NNTP (Network News Transfer Protocol) protocol - a network news transfer protocol.

Teleconferences allow discussion of any topic, and everyone is free to express their opinion, observing a certain etiquette.

Today Usenet has more than ten thousand discussion groups (NewsGroups) or newsgroups, each of which is devoted to a specific topic and is a means of exchanging opinions.

Remote access service for computers.

The TELNET remote access service allows you to log in to another Internet-based computer system using the TELNET protocol.

This program consists of two components: a client program that runs on the client computer and a server program that runs on the server computer.

Functions of the client program:

establishing a connection with the server;

receiving input data from the subscriber, converting them to a standard format and sending them to the server;

receiving query results from the server in a standard format and reformatting them into a form convenient for the client.

Functions of the server program:

waiting for a request in a standard form;

serving this request;

sending the results to the client program.

Telnet is a simple and therefore universal means of communication on the Internet.

On the Internet, the same network node can simultaneously work on several protocols. Therefore, large network nodes now have a complete set of servers, and they can be accessed using almost any of the existing protocols.

Web service.

Web service, web service (English web service) - a software system identified by a web address with standardized interfaces.

Web services can communicate with each other and with third-party applications through messages based on certain protocols (SOAP, XML-RPC, REST, etc.). A web service is the unit of modularity when using a service-oriented application architecture.

In everyday life, web services are called services provided on the Internet. In this usage, the term needs to be clarified whether it refers to searching, web mail, storing documents, files, bookmarks, etc. These web services can be used regardless of the computer, browser or Internet access point.

Architecture

There are three instances that interact within a web service.

customer (service requestor);

performer (service provider);

directory (service broker).

When a service is developed, the vendor registers it in a directory where it can be found by potential customers. The customer, having found a suitable service in the catalog, imports its WSDL specification from there and develops his software in accordance with it. WSDL describes the format of requests and responses that are exchanged between the customer and the performer in the course of work. The following standards are used to ensure interoperability:

XML: Extensible Markup Language for storing and communicating structured data;

SOAP: XML Based Messaging Protocol;

WSDL: XML-based Web Service External Interface Description Language;

UDDI: Universal Discovery, Description and Integration Interface. A directory of Web Services and information about companies that provide Web Services to the public or to specific companies. While UDDI exists, however, only in small proprietary networks and has not yet found wide distribution on the open Internet.

Development Methods

There are web service development automation tools that fall into two main groups. In bottom-up development, implementation classes are written first, and WSDL files documenting the service are generated from their source code. The disadvantage of this method is that Java classes are subject to frequent changes. The top-down approach first prepares the WSDL and generates the skeleton of the Java class that implements the service from it. This path is considered more difficult, but leads to cleaner and better protected solutions. As long as the format of the messages exchanged between the customer and the contractor does not change, changes in each of them do not disrupt the interaction. This technique is sometimes referred to as “contract first”, since the starting point is the WSDL (“contract” between the customer and the contractor).

Advantages.

Web services enable interaction between software systems regardless of platform. For example, a Windows-C# client can communicate with a Java server running under Linux.

Web services are based on open standards and protocols. Using XML makes it easy to develop and debug web services.

The use of the Internet protocol provides HTTP interaction between software systems through a firewall. This is a significant advantage over technologies such as CORBA, DCOM or Java RMI. On the other hand, web services are not tightly bound to HTTP - other protocols can be used.

disadvantages

Lower performance and larger network traffic compared to RMI, CORBA, DCOM technologies due to the use of XML text messages. However, some web servers can be configured to compress network traffic.

Aspects of security. Responsible web services should use encryption, possibly requiring user authentication. Whether HTTPS is sufficient, or whether solutions such as XML Signature, XML Encryption, or SAML are preferred, is up to the developer to decide.

Network security.

Network security is an applied scientific discipline, a branch of computer science.

Deals with issues of ensuring the information security of a computer network and its resources, in particular, data stored in it and transmitted through it, and users working with it. It is an extension of computer security (as a discipline) and a subsection of information security. Engaged in the study and development of methods and practical rules for working with the network, including protocols for communication and data exchange and cryptographic methods for protecting information.

Among the risks to which a computer network is exposed and the prevention of which is the goal of network security as a discipline are: unauthorized access to network resources (for example, unauthorized reading of files) and prevention of attacks, the purpose of which is to disable certain services provided by the network (for example, preventing all or part of users to view the company website).

In addition to discipline, the term "network security" can be understood as a set of procedures, standards, rules and tools designed to ensure the security of a computer network. Among both hardware and software tools, and devices used for this purpose: firewalls (firewalls), antivirus programs, network monitoring tools, means for detecting unauthorized access attempts (intrusions), proxy servers and authentication servers.

Ensuring network security is an important aspect of any company's activity.

Firewalls.

A firewall is a set of hardware and software in a computer network that controls and filters network packets passing through it in accordance with specified rules.

The main task of the firewall is to protect the network or its individual nodes from unauthorized access. Also, firewalls are often called filters, since their main task is not to let through (filter) packets that do not meet the criteria defined in the configuration.

Some firewalls also allow address translation - dynamic replacement of internal (gray) addresses or ports with external ones used outside the local network, which can provide additional security.

Other names.

Firewall (German: Brandmauer) is a term borrowed from the German language, which is an analogue of the English firewall in its original meaning (a fire barrier is a wall that separates adjacent buildings, preventing the spread of fire). Interestingly, in the field of computer technology in German, the word Firewall is used.

Firewall, firewall, firewall, firewall - formed by transcription of the English term firewall.

Types of network screens.

The supported layer of the OSI network model is the main characteristic in classifying firewalls. There are the following types of firewalls:

Managed switches (link layer).

Network layer network filters (stateless). Filtering is static, carried out by analyzing the source and destination IP addresses, protocol, source and destination ports.

Session level gateways (circuit-level proxy). In the TCP / IP network model, there is no level that uniquely corresponds to the OSI session layer, therefore, filters that cannot be identified with either the network, or the transport, or the application layer are classified as session-level gateways:

gateways that translate addresses (NAT, PAT) or network protocols (translating bridge);

channel state control filters. The filters for monitoring the state of the communication channel often include network-level network filters with advanced features (stateful), which additionally analyze packet headers and are able to filter fragmented packets);

session level gateways. The most well-known and popular session layer gateway is the SOCKS intermediary.

Application level gateway (application-level proxy), often referred to as proxy servers. They are divided into transparent (transparent) and opaque (solid).

The SPI (Stateful Packet Inspection, SPI) firewall, or otherwise, firewalls with dynamic packet filtering (Dynamic Packet Filtering), are essentially gateways

session layer with advanced features. State inspectors operate at the session layer, but "understand" application and network layer protocols. Unlike an application layer gateway that opens two TCP virtual circuits (one for the client and one for the server) for each connection, the state inspector does not prevent a direct connection between the client and the server.

There is also the concept of "expert-level firewall". Firewalls of this type are based on application-level intermediaries or state inspectors, but are necessarily equipped with session-level gateways and network filters, sometimes understanding the network level as well. Often they have a system for logging events and notifying administrators, tools for supporting remote users (for example, authorization), tools for building virtual private networks, etc. Almost all firewalls on the market belong to it.

typical possibilities.

Filtering access to known insecure services.

Preventing the receipt of sensitive information from the protected subnet, as well as the introduction of false data into the protected subnet using vulnerable services.

Access control to network nodes.

It can register all access attempts both from the outside and from the internal network, which allows you to keep track of the use of Internet access by individual network nodes.

Regulation of the order of access to the network.

Notification of suspicious activity, attempts to probe or attack on hosts or the screen itself.

Due to security restrictions, some services required by the user, such as Telnet, FTP, SMB, NFS, and so on, may be blocked. Therefore, setting up a firewall requires the participation of a network security specialist. Otherwise, the harm from misconfiguration may outweigh the benefits.

It should also be noted that using a firewall increases response time and reduces throughput, since filtering is not instantaneous.

Problems not solved by the firewall.

A firewall by itself is not a panacea for all network threats. In particular, he:

does not protect network nodes from penetration through the back doors or software vulnerabilities;

does not provide protection against many internal threats, primarily data leaks;

does not prevent users from downloading malware, including viruses.

To solve the last two problems, appropriate additional tools are used, in particular, antiviruses. Usually they connect to the firewall and pass through themselves the appropriate part of the network traffic, working as a transparent proxy for other network nodes, or they receive a copy of all transmitted data from the firewall. However, such an analysis requires significant hardware resources, so it is usually carried out on each node of the network independently.

Similar information.

Internet resources: tools and tools for creating and developing a business

Each Internet resource has its own functions and value, which can be used to build a successful Internet business.

What are they and what are they used for??...

When the Global Network is chosen as the main place of activity, the need for Internet resources is obvious. Only with their help you can break through to the target audience, provide the necessary information, get a response, make sales, and make a profit.

Types of Internet resources

There is a huge number of Internet resources, all of them perform typical functions, according to which they can be used in business:

1. Internet resource - Website. An information resource that is dedicated to a particular company, phenomenon, topic, event, and so on.
2. Internet resource - Community in a social network. Resources on which a group of people is registered, interested in one idea, having common views. The community posts information on a specific topic or several topics, and discussions are held.
3. Internet resource - Blog. Thematic Internet resource, usually owned by one person. Here articles are published, as a rule, on a certain narrow topic. The functionality plan usually provides for the ability to leave comments and communicate.
4. Internet resource - One-pager. A resource consisting of one page, capaciously and clearly revealing one specific topic, talking about a product, service, phenomenon, person.
5. Internet resource - Portal or network of sites. An informational or interactive resource that involves a large number of visitors and heavy traffic. The entire network has a common domain name.
6. Internet resource - Internet service. This is a resource that looks like directories, storage or exchanger.
7. Internet resource - Newsletter. This resource does not have a domain name, but is a tool that is capable of mass informing.

Understanding the possibilities each Internet resource and knowing how to use them to your advantage, much more likely build a successful and profitable business that will be known to thousands and even millions of people.

Online resources are business opportunities that work for you!