Notes for Cyber Crime

What is Cyber Crime?

Before starting our discussion first we must know what “Cyber crime” is and what are the impacts and the benefits the “Cyber Criminals” gain from such activities.

Definition of Cyber Crime:

“Any crime that involves a computer and a network is called a "Computer Crime"

For this purpose a computer may have been used to commit such crime or simply a computer may be the target.

Another term called “Internet crime” refers to criminal activities for exploiting the internet. These crimes include and are not limited to identity theft, threatening a nation’s security, copyright infringement and child pornography. These crimes have become a threat to individual privacy, where confidential data, individual’s identity or photos and videos etc. is stolen or intercepted by the attacker.

In “Cyber Crime” such as identity theft, financial theft, espionage mostly non-state agents and government organizations are involved.

For example, in the latest turn of events the National Security Agency (NSA) of the United States was held responsible for intercepting and spying on millions of online users.

Or in another example, the Chinese hackers were involved in constantly hacking into Big US organizations and agencies like the latest attack on the New York Times in January 2013.

Such criminal activities carried out online involving nations and state missionary is known as “Cyber Warfare”.

Types of Cyber Crimes

1. Cyber Crimes against Persons

2. Cyber Crimes against Persons Property

3. Cyber Crimes against Government

4. Cyber Crimes against Society

The following are the description of all the types of Cyber Crimes.

1. Cyber Crimes against Persons

There are certain offences which affect the personality of individuals can be defined as:

1. Harassment via E-Mails: It is very common type of harassment through sending letters, attachments of files & folders i.e. via e-mails. At present harassment is common as usage of social sites i.e. Facebook, Twitter etc. increasing day by day.

2. Cyber-Stalking: It means expressed or implied a physical threat that creates fear through the use to computer technology such as internet, e-mail, phones, text messages, webcam, websites or videos.

3. Dissemination of Obscene Material: It includes Indecent exposure/ Pornography (basically child pornography), hosting of web site containing these prohibited materials. These obscene matters may cause harm to the mind of the adolescent and tend to deprave or corrupt their mind.

4. Defamation: It is an act of imputing any person with intent to lower down the dignity of the person by hacking his mail account and sending some mails with using vulgar language to unknown persons mail account.

5. Hacking: It means unauthorized control/access over computer system and act of hacking completely destroys the whole data as well as computer programmes. Hackers usually hacks telecommunication and mobile network.

6. Cracking: It is amongst the gravest cyber crimes known till date. It is a dreadful feeling to know that a stranger has broken into your computer systems without your knowledge and consent and has tampered with precious confidential data and information.

7. E-Mail Spoofing: A spoofed e-mail may be said to be one, which misrepresents its origin. It shows it’s origin to be different from which actually it originates.

8. SMS Spoofing: Spoofing is a blocking through spam which means the unwanted uninvited messages. Here a offender steals identity of another in the form of mobile phone number and sending SMS via internet and receiver gets the SMS from the mobile phone number of the victim. It is very serious cyber crime against any individual.

9.Carding: It means false ATM cards i.e. Debit and Credit cards used by criminals for their monetary benefits through withdrawing money from the victim’s bank account mala-fidely. There is always unauthorized use of ATM cards in this type of cyber crimes.

10. Cheating & Fraud: It means the person who is doing the act of cyber crime i.e. stealing password and data storage has done it with having guilty mind which leads to fraud and cheating.

11. Child Pornography: It involves the use of computer networks to create, distribute, or access materials that sexually exploit underage children.

12. Assault by Threat: refers to threatening a person with fear for their lives or lives of their families through the use of a computer network i.e. E-mail, videos or phones.

2. Cyber Crimes against Persons Property:

As there is rapid growth in the international trade where businesses and consumers are increasingly using computers to create, transmit and to store information in the electronic form instead of traditional paper documents. There are certain offences which affects person’s properties which are as follows:

1. Intellectual Property Crimes: Intellectual property consists of a bundle of rights. Any unlawful act by which the owner is deprived completely or partially of his rights is an offence. The common form of IPR violation may be said to be software piracy, infringement of copyright, trademark, patents, designs and service mark violation, theft of computer source code, etc.

2. Cyber Squatting: It means where two persons claim for the same Domain Name either by claiming that they had registered the name first on by right of using it before the other or using something similar to that previously. For example two similar names i.e. www.yahoo.com and www.yaahoo.com.

3. Cyber Vandalism: Vandalism means deliberately destroying or damaging property of another. Thus cyber vandalism means destroying or damaging the data when a network service is stopped or disrupted. It may include within its purview any kind of physical harm done to the computer of any person. These acts may take the form of the theft of a computer, some part of a computer or a peripheral attached to the computer.

4. Hacking Computer System: Hacktivism attacks those included Famous Twitter, blogging platform by unauthorized access/control over the computer. Due to the hacking activity there will be loss of data as well as computer. Also research especially indicates that those attacks were not mainly intended for financial gain too and to diminish the reputation of particular person or company.

5. Transmitting Virus: Viruses are programs that attach themselves to a computer or a file and then circulate themselves to other files and to other computers on a network. They usually affect the data on a computer, either by altering or deleting it. Worm attacks plays major role in affecting the computerize system of the individuals.

6. Cyber Trespass: It means to access someone’s computer without the right authorization of the owner and does not disturb, alter, misuse, or damage data or system by using wireless internet connection.

7. Internet Time Thefts: Basically, Internet time theft comes under hacking. It is the use by an unauthorized person, of the Internet hours paid for by another person. The person who gets access to someone else’s ISP user ID and password, either by hacking or by gaining access to it by illegal means, uses it to access the Internet without the other person’s knowledge. You can identify time theft if your Internet time has to be recharged often, despite infrequent usage.

3. Cyber Crimes against Government:

There are certain offences done by group of persons intending to threaten the international governments by using internet facilities. It includes:

1.Cyber Terrorism: Cyber terrorism is a major burning issue in the domestic as well as global concern. The common form of these terrorist attacks on the Internet is by distributed denial of service attacks, hate websites and hate e-mails, attacks on sensitive computer networks etc. Cyber terrorism activities endanger the sovereignty and integrity of the nation.

2. Cyber Warfare: It refers to politically motivated hacking to conduct sabotage and espionage. It is a form of information warfare sometimes seen as analogous to conventional warfare although this analogy is controversial for both its accuracy and its political motivation.

3. Distribution of pirated software: It means distributing pirated software from one computer to another intending to destroy the data and official records of the government.

4. Possession of Unauthorized Information: It is very easy to access any information by the terrorists with the aid of internet and to possess that information for political, religious, social, ideological objectives.

4. Cyber Crimes against Society at large:

An unlawful act done with the intention of causing harm to the cyberspace will affect large number of persons. This offence includes

1.Child Pornography: It involves the use of computer networks to create, distribute, or access materials that sexually exploit underage children. It also includes activities concerning indecent exposure and obscenity.

2. Cyber Trafficking: It may be trafficking in drugs, human beings, arms weapons etc. which affects large number of persons. Trafficking in the cyberspace is also a gravest crime.

3. Online Gambling: Online fraud and cheating is one of the most lucrative businesses that are growing today in the cyber space. There are many cases that have come to light are those pertaining to credit card crimes, contractual crimes, offering jobs, etc.

4.Financial Crimes: This type of offence is common as there is rapid growth in the users of networking sites and phone networking where culprit will try to attack by sending bogus mails or messages through internet. Ex: Using credit cards by obtaining password illegally.

5.Forgery: It means to deceive large number of persons by sending threatening mails as online business transactions are becoming the habitual need of today’s life style.

What is a Hacker?

“A hacker is someone who breaks into computer or a computer network”.

                Hackers are motivated to commit such crimes either for financial gains, protesting against any political activity or just to challenge the limits of his skills and expertise in the field. Not all hackers show theirs skills in performing criminal activities. Some hackers look for loophole & backdoors in software and websites, and if any vulnerabilities are found they report back to the owner or the authorities. One such example happened recently when a young Palestinian hacker found a bug in Facebook and he reported that bug to the authorities. But unfortunately he wasn’t given any credit or reward for showing his skills and good intentions.

                That’s how experts distinguish Hackers from Crackers. A hacker is someone who carries out such activities with good intentions and a cracker do the same but his main objective is to cause harm.

INTELLECTUAL PROPERTY RIGHTS(UNIT 1)

INTELLECTUAL PROPERTY RIGHTS

WHAT IS AN IPR?

 Intellectual Property Rights are legal rights, which result from intellectual activity in industrial, scientific, literary & artistic fields. These rights Safeguard creators and other producers of intellectual goods & services by granting them certain time-limited rights to control their use. Protected IP rights like other property can be a matter of trade, which can be owned, sold or bought. These are intangible and non exhausted consumption.

TYPES/TOOLs OF IPRs:

a. Patents.

b. Trademarks.

c. Copyrights and related rights.

d. Geographical Indications.

e. Industrial Designs.

f. Trade Secrets.

g. Layout Design for Integrated Circuits.

h. Protection of New Plant Variety.

1) Patent

A patent is an exclusive right granted for an invention, which is a product or a process that provides a new way of doing something, or offers a new technical solution to a problem. It provides protection for the invention to the owner of the patent. The protection is granted for a limited period, i.e 20 years. Patent protection means that the invention cannot be commercially made, used, distributed or sold without the patent owner's consent. A patent owner has the right to decide who may - or may not - use the patented invention for the period in which the invention is protected. The patent owner may give permission to, or license, other parties to use the invention on mutually agreed terms. The owner may also sell the right to the invention to someone else, who will then become the new owner of the patent. Once a patent expires, the protection ends, and an invention enters the public domain, that is, the owner no longer holds exclusive rights to the invention, which becomes available to commercial exploitation by others.

 All patent owners are obliged, in return for patent protection, to publicly disclose information on their invention in order to enrich the total body of technical knowledge in the world. Such an ever-increasing body of public knowledge promotes further creativity and innovation in others. In this way, patents provide not only protection for the owner but valuable information and inspiration for future generations of researchers and inventors.

2)Trademarks:

A trademark is a distinctive sign that identifies certain goods or services as those produced or provided by a specific person or enterprise. It may be one or a combination of words, letters, and numerals. They may consist of drawings, symbols, three- dimensional signs such as the shape and packaging of goods, audible signs such as music or vocal sounds, fragrances, or colours used as distinguishing features.

 It provides protection to the owner of the mark by ensuring the exclusive right to use it to identify goods or services, or to authorize another to use it in return for payment. It helps consumers identify and purchase a product or service because its nature and quality, indicated by its unique trademark, meets their needs. Registration of trademark is prima facie proof of its ownership giving statutory right to the proprietor.

Trademark rights may be held in perpetuity. The initial term of registration is for 10 years; thereafter it may be renewed from time to time.

3)Copyrights and related rights:

 Copyright is a legal term describing rights given to creators for their literary and artistic works. The kinds of works covered by copyright include: literary works such as novels, poems, plays, reference works, newspapers and computer programs; databases; films, musical compositions, and choreography; artistic works such as 3 paintings, drawings, photographs and sculpture; architecture; and advertisements, maps and technical drawings.

Copyright subsists in a work by virtue of creation; hence it’s not mandatory to register. However, registering a copyright provides evidence that copyright subsists in the work & creator is the owner of the work. Creators often sell the rights to their works to individuals or companies best able to market the works in return for payment.

 These payments are often made dependent on the actual use of the work, and are then referred to as royalties. These economic rights have a time limit, (other than photographs) is for life of author plus sixty years after creator’s death.

4)Geographical Indications (GI):

GI are signs used on goods that have a specific geographical origin and possess qualities or a reputation that are due to that place of origin. Agricultural products typically have qualities that derive from their place of production and are influenced by specific local factors, such as climate and soil. They may also highlight specific qualities of a product, which are due to human factors that can be found in the place of origin of the products, such as specific manufacturing skills and traditions.

 A geographical indication points to a specific place or region of production that determines the characteristic qualities of the product that originates therein. It is important that the product derives its qualities and reputation from that place. Place of origin may be a village or town, a region or a country.

It is an exclusive right given to a particular community hence the benefits of its registration are shared by the all members of the community. Recently the GIs of goods like Chanderi Sarees, Kullu Shawls, Wet Grinders etc have been registered. Keeping in view the large diversity of traditional products spread all over the country, the registration under GI will be very important in future growth of the tribes / communities / skilled artisans associated in developing such products.

5)Industrial Designs:

Industrial designs refer to creative activity, which result in the ornamental or formal appearance of a product, and design right refers to a novel or original design that is accorded to the proprietor of a validly registered design. Industrial designs are an element of intellectual property.

Under the TRIPS Agreement, minimum standards of protection of industrial designs have been provided for. As a developing country, India has already amended its national legislation to provide for these minimal standards.

The essential purpose of design law it to promote and protect the design element of industrial production. It is also intended to promote innovative activity in the field of industries. The existing legislation on industrial designs in India is contained in the New Designs Act, 2000 and this Act will serve its purpose well in the rapid changes in technology and international developments. India has also achieved a mature status in the field of industrial designs and in view of globalization of the economy, the present legislation is aligned with the changed technical and commercial scenario and made to conform to international trends in design administration.

This replacement Act is also aimed to enact a more detailed classification of design to conform to the international system and to take care of the proliferation of design related activities in various fields.

6)Trade Secrets:

It may be confidential business information that provides an enterprise a

competitive edge may be considered a trade secret. Usually these are manufacturingor industrial secrets and commercial secrets. These include sales methods, distributionmethods, consumer profiles, advertising strategies, lists of suppliers and clients, and manufacturing processes. Contrary to patents, trade secrets are protected without registration.

A trade secret can be protected for an unlimited period of time but a

substantial element of secrecy must exist, so that, except by the use of improper

means, there would be difficulty in acquiring the information.

 Considering the vast availability of traditional knowledge in the country the protection under this will be very crucial in reaping benefits from such type of knowledge. The Trades secret, traditional knowledge are also interlinked / associated with the geographical indications.

7) Layout Design for Integrated Circuits:

Semiconductor Integrated Circuit means a product having transistors and

other circuitry elements, which are inseparably formed on a semiconductor material or an insulating material or inside the semiconductor material and designed to perform an electronic circuitry function.

The aim of the Semiconductor Integrated Circuits Layout-Design Act 2000 is

to provide protection of Intellectual Property Right (IPR) in the area of

Semiconductor Integrated Circuit Layout Designs and for matters connected

There with or incidental thereto. The main focus of SICLD Act is to provide for routes and mechanism for protection of IPR in Chip Layout Designs created and matters related to it.

The SICLD Act empowers the registered proprietor of the layout-design an inherent right to use the layout-design, commercially exploit it and obtain relief in respect of any infringement. The initial term of registration is for 10 years; thereafter it may be renewed from time to time.

Department of Information Technology Ministry of Communications and Information Technology is the administrative ministry looking after its registration and other matters.

Notes for Simple Mail Transfer Protocol (SMTP)

Simple Mail Transfer Protocol (SMTP)

·         The actual mail transfer is done through message transfer agents (MTAs).

·         To send mail,a system must have the client MTA, and to receive mail, a system must have a server MTA.

·         The formal protocol that defines the MTA client and server in the Internet is called Simple Mail Transfer Protocol (SMTP).

·         Following fig. Shows the scenario of SMTP protocol.

·         SMTP is used two times, between the sender and the sender’s mail server and

     between the two mail servers.

·         Commands and Responses

·         SMTP uses commands and responses to transfer messages between an MTA client and

an MTA server as shown in following fig.

·         Each command or reply is terminated by a two-character end-of-line token.

·         Commands

·         Commands are sent from the client to the server. The format of a command is shown below:

·         Keyword: argument(s)

·         It consists of a keyword followed by zero or more arguments. SMTP defines 14

commands listed in following Table and described in more detail below.

·         HELO. This command is used by the client to identify itself. The argument is the

domain name of the client host. The format is HELO: challenger.atc.fhda.edu

·         MAIL FROM. This command is used by the client to identify the sender of the

message. The argument is the e-mail address of the sender (local part plus the

domain name). The format isMAIL FROM: forouzan@challenger.atc.fhda.edu

·         RCPT TO. This command is used by the client to identify the intended recipient of

the message. The argument is the e-mail address of the recipient. If there are multiple

recipients, the command is repeated. The format isRCPT TO: betsy@mcgraw-hill.com

·         DATA. This command is used to send the actual message. All lines that follow the

DATA command are treated as the mail message. The message is terminated by a

line containing just one period. The format isDATA

This is the message

to be sent to the McGraw-Hill

Company.

·         QUIT. This command terminates the message. The format is QUIT

·         RSET. This command aborts the current mail transaction. The stored information

about the sender and recipient is deleted. The connection will be reset. RSET

·         VRFY. This command is used to verify the address of the recipient, which is sent

as the argument. The sender can ask the receiver to confirm that a name identifies a

valid recipient. Its format isVRFY: betsy@mcgraw-hill.com

·         NOOP. This command is used by the client to check the status of the recipient. It

requires an answer from the recipient. Its format isNOOP

·         TURN. This command lets the sender and the recipient switch positions, whereby

the sender becomes the recipient and vice versa. However, most SMTP implementations

today do not support this feature. The format isTURN

·         EXPN. This command asks the receiving host to expand the mailing list sent as the

arguments and to return the mailbox addresses of the recipients that comprise the

list. The format isEXPN: x y z

·         HELP. This command asks the recipient to send information about the command

sent as the argument. The format isHELP: mail

·         SEND FROM. This command specifies that the mail is to be delivered to the

terminal of the recipient, and not the mailbox. If the recipient is not logged in,

the mail is bounced back. The argument is the address of the sender. The

format isSEND FROM: forouzan@fhda.atc.edu

·         SMOL FROM. This command specifies that the mail is to be delivered to the terminal

or the mailbox of the recipient. This means that if the recipient is logged in, the mail is         delivered only to the terminal. If the recipient is not logged in, the mail is

delivered to the mailbox. The argument is the address of the sender. The format is

·         SMOL FROM: forouzan@fhda.atc.edu

·         SMAL FROM. This command specifies that the mail is to be delivered to the terminal

and the mailbox of the recipient. This means that if the recipient is logged in,

the mail is delivered to the terminal and the mailbox. If the recipient is not logged

in, the mail is delivered only to the mailbox. The argument is the address of the

sender. The format is SMAL FROM: forouzan@fhda.atc.edu

·         Responses

Responses are sent from the server to the client. A response is a three-digit code that

may be followed by additional textual information.

Following Table  lists some of the responses.

·         Mail Transfer Phases

·         The process of transferring a mail message occurs in three phases: connection establishment,mail transfer, and connection termination.

i)                    Connection Establishment

After a client has made a TCP connection to the well-known port 25, the SMTP server

starts the connection phase. This phase involves the following three steps, which are

illustrated in Fig.

1.  The server sends code 220 (service ready) to tell the client that it is ready to receive

mail. If the server is not ready, it sends code 421 (service not available).

2.  The client sends the HELO message to identify itself using its domain name

address. This step is necessary to inform the server of the domain name of the

client. Remember that during TCP connection establishment, the sender and

receiver know each other through their IP addresses.

3.  The server responds with code 250 (request command completed) or some other

code depending on the situation.

i)                    Message Transfer

After connection has been established between the SMTP client and server, a single

message between a sender and one or more recipients can be exchanged. This phase

involves eight steps. Steps 3 and 4 are repeated if there is more than one recipient (see

in Fig.).

1.  The client sends the MAIL FROM message to introduce the sender of the message.

It includes the mail address of the sender (mailbox and the domain name). This

step is needed to give the server the return mail address for returning errors and

reporting messages.

2.  The server responds with code 250 or some other appropriate code.

3.  The client sends the RCPT TO (recipient) message, which includes the mail

address of the recipient.

4.  The server responds with code 250 or some other appropriate code.

5.  The client sends the DATA message to initialize the message transfer.

6.  The server responds with code 354 (start mail input) or some other appropriate

message.

7.  The client sends the contents of the message in consecutive lines. Each line is terminated

by a two-character end-of-line token (carriage return and line feed). The

message is terminated by a line containing just one period.

8.  The server responds with code 250 (OK) or some other appropriate code.

i)                    Connection Termination

1 After the message is transferred successfully, the client terminates the connection. This

phase involves two steps (see Fig).

2  The client sends the QUIT command.

3 The server responds with code 221 or some other appropriate code.

After the connection termination phase, the TCP connection must be closed.

E-Mail Protocol Notes

Electronic Mail

The most popular Internet services are electronic mail (e-mail).

At the beginning of the Internet era, the messages sent by electronic mail were short and consisted of text only; they let people exchange quick memos.

Today, electronic mail is much more complex. It allows a message to include text, audio, and video. It also allows one message to be sent to one or more recipients.

Architecture of E-mail

There are four scenarios: First Scenario, Second Scenario, Third Scenario, and Fourth Scenario.

1.      First Scenario:

·         In the first scenario, the sender and the receiver of the e-mail are on the same mail server, they are directly connected to a shared mail server.

·         The administrator has created one mailbox for each user where the received messages are stored.

·         A mailbox is part of a local hard drive, a special file with permission restrictions. Only the owner of the mailbox has access to it.

·         When Alice needs to send a message to Bob, she runs a user agent (UA) program to prepare the message and store it in Bob’s mailbox.

·         The message has the sender and recipient mailbox addresses.

·         Bob can retrieve and read the contents of his mailbox at his convenience using a user agent.

·         Following fig. Shows the concept

·         Example: This is similar to the traditional letter exchange between two people. There is a letter box where each person has a letter with his or her name on it. When Alice needs to send a letter to Bob, she writes the letter and inserts it into Bob’s letterbox. When Bob checks his letter box, he finds Alice’s letter and reads it.

2.      Second Scenario :

·         In the second scenario, the sender and the receiver of the e-mail are users on two different mail servers.

·         The message needs to be sent over the Internet. Here we need user agents (UAs) and message transfer agents (MTAs) as shown in following Fig.

·         Alice needs to use a user agent program to send her message to the mail server at her own site.

·         The mail server at her site uses a queue (spool) to store messages waiting to be sent.

·         Bob also needs a user agent program to retrieve messages stored in the mailbox of the system at his site.

·         The message, however, needs to be sent through the Internet from Alice’s site to Bob’s site.

·         Here two message transfer agents are needed: one client and one server. Like most client-server programs on the Internet, the server needs to run all of the time because it does not know when a client will ask for a connection.

·         The client, on the other hand, can be triggered by the system when there is a message in the queue to be sent.

3.      Third Scenario :

·         When the sender is connected to the mail server via a LAN or a WAN, we need two UAs and two pairs of MTAs (client and server).

·         As shows in fig. Bob, as in the second scenario, is directly connected to his mail server.

·         Alice, however, is separated from her mail server.

·         Alice is either connected to the mail server via a point-to-point WAN—such as a dial-up modem, a DSL, or a cable modem—or she is connected to a LAN in an organization that uses one mail server for handling e-mails, all users need to send their messages to this mail server.

·         Alice still needs a user agent to prepare her message. She then needs to send the message through the LAN or WAN.

·         This can be done through a pair of message transfer agents (client and server).

·         Whenever Alice has a message to send, she calls the user agent which, in turn, calls the MTA client. The MTA client establishes a connection with the MTA server on the system, which is running all the time.

·         The system at Alice’s site queues all messages received. It then uses an MTA client to send the messages to the system at Bob’s site; the system receives the message and stores it in Bob’s mailbox.

4.       Fourth Scenario :

·         When both sender and receiver are connected to the mail server via a LAN or a WAN, we need two UAs, two pairs of MTAs (client and server), and a pair of MAAs (client and server).

·         This is the most common situation today.

·         As shows in fig. Bob is also connected to his mail server by a WAN or a LAN.

·         After the message has arrived at Bob’s mail server, Bob needs to retrieve it.

·         Here, we need another set of client-server agents, which we call message access agents (MAAs). Bob uses an MAA client to retrieve his messages.

·         The client sends a request to the MAA server, which is running all the time, and requests the transfer of the messages.

·         The situation is shown in Fig. There are two important points we need to emphasize here.

·         First, Bob cannot bypass the mail server and use the MTA server directly.

·         To use the MTA server directly, Bob would need to run the MTA server all the time because he does not know when a message will arrive.

·         This implies that Bob must keep his computer on all the time if he is connected to his system through a LAN.

·         If he is connected through a WAN, he must keep the connection up all the time. Neither of these situations is feasible today.

·         Second, note that Bob needs another pair of client-server programs: message access programs. This is because an MTA client-server program is a push program: the client pushes the message to the server. Bob needs a pull program. The client needs to pull the message from the server. Following fig.  Shows the difference.

User Agent:

It provides service to the user to make the process of sending and receiving a message easier.

Services Provided by a User Agent:

A user agent is a software package (program) that composes, reads, replies to, and forwards Messages. It also handles local mailboxes on the user computers.

User Agent Types

There are two types of user agents: command-driven and GUI-based.

command-driven:

A command-driven user agent normally accepts a onecharacter

command from the keyboard to perform its task. For example, a user can type

the character r, at the command prompt, to reply to the sender of the message, or type

the character R to reply to the sender and all recipients.

Some examples of command-driven user agents are mail, pine, and elm.

GUI-based:

Modern user agents are GUI-based. They contain graphical user interface (GUI)

components that allow the user to interact with the software by using both the keyboard

and the mouse. They have graphical components such as icons, menu bars, and windows

that make the services easy to access.

Some examples of GUI-based user agents are Eudora, Outlook, and Netscape.

Sending Mail

To send mail, the user, through the UA, creates mail that looks very similar to postal

mail.

It has an envelope and a message as shown in following fig.

Envelope

The envelope usually contains the sender address, the receiver address, and other

information.

Message

The message contains the header and the body.

The header of the message defines thesender, the receiver, the subject of the message, and some other information.

The body of the message contains the actual information to be read by the recipient.

Receiving Mail

The user agent is triggered by the user (or a timer). If a user has mail, the UA informs

the user with a notice.

 If the user is ready to read the mail, a list is displayed in which each line contains a summary of the information about a particular message in the mailbox.

The summary usually includes the sender mail address, the subject, and the time

the mail was sent or received.

The user can select any of the messages and display its contents on the screen.

Addresses

To deliver mail, a mail handling system must use an addressing system with unique

addresses.

 In the Internet, the address consists of two parts: a local part and a domain

name, separated by an @ sign as shown in fig.

Local Part

The local part defines the name of a special file, called the user mailbox, where all of

the mail received for a user is stored for retrieval by the message access agent.

Domain Name

The second part of the address is the domain name. An organization usually selects

one or more hosts to receive and send e-mail; they are sometimes called mail servers

or exchangers. The domain name assigned to each mail exchanger either comes from

the DNS database or is a logical name (for example, the name of the organization).

Mailing List or Group List

Electronic mail allows one name, an alias, to represent several different e-mail

addresses; this is called a mailing list. Every time a message is to be sent, the system

checks the recipient’s name against the alias database; if there is a mailing list

for the defined alias, separate messages, one for each entry in the list, must be prepared

and handed to the MTA. If there is no mailing list for the alias, the name

itself is the receiving address and a single message is delivered to the mail transfer

entity.