internet & computer security exercise - 10 · it workshop lab manual 180 approved by :...

IT WORKSHOP LAB MANUAL

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Mr.V.S.V.S.S.S.M.CHAKRADHAR

Internet & Computer Security

Exercise - 10

Aim: Introduction to computer networking, demonstration on network components,

drivers loading and configuration settings, mapping of IP addresses, configuration of

Internet and Wi-Fi.

10.1 Introduction to Types of Networks

One way to categorize the different types of computer network designs is by their scope or scale.

For historical reasons, the networking industry refers to nearly every type of design as some kind

of area network. Common examples of area network types are:

LAN - Local Area Network

WLAN - Wireless Local Area Network

WAN - Wide Area Network

MAN - Metropolitan Area Network

SAN - Storage Area Network, System Area Network, Server Area Network, or

sometimes Small Area Network

CAN - Campus Area Network, Controller Area Network, or sometimes Cluster Area

Network

PAN - Personal Area Network

DAN - Desk Area Network

LAN and WAN were the original categories of area networks, while the others have gradually

emerged over many years of technology evolution. Note that these network types are a separate

concept from network topologies such as bus, ring and star.

Topology in Network Design

Network topologies are categorized into the following basic types:

bus

ring

star

tree

mesh

More complex networks can be built as hybrids of two or more of the above basic topologies.


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Bus Topology

Bus networks use a common backbone to connect all devices. A single cable, the backbone

functions as a shared communication medium that devices attach or tap into with an interface

connector.

Fig. 1. Bus Topology

Ring Topology

In a ring network, every device has exactly two neighbors for communication purposes. All

messages travel through a ring in the same direction (either "clockwise" or "counterclockwise").

A failure in any cable or device breaks the loop and can take down the entire network.

Fig. 2. Ring Topology

Star Topology

Many home networks use the star topology. A star network features a central connection point

called a "hub" that may be a hub, switch or router. Devices typically connect to the hub with

Unshielded Twisted Pair (UTP) Ethernet.

http://compnetworking.about.com/cs/internetworking/g/bldef_hub.htm

http://compnetworking.about.com/od/hardwarenetworkgear/g/bldef_switch.htm

http://compnetworking.about.com/cs/routers/g/bldef_router.htm


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Fig. 3. Star Topology

Tree Topology

Tree topologies integrate multiple star topologies together onto a bus. In its simplest form, only

hub devices connect directly to the tree bus, and each hub functions as the "root" of a tree of

devices. This bus/star hybrid approach supports future expandability of the network much better

than a bus (limited in the number of devices due to the broadcast traffic it generates) or a star

(limited by the number of hub connection points) alone.

Fig. 4. Tree Topology

Mesh Topology

Mesh topologies involve the concept of routes. Unlike each of the previous topologies, messages

sent on a mesh network can take any of several possible paths from source to destination. (Recall

that even in a ring, although two cable paths exist, messages can only travel in one direction.)

Some WANs, most notably the Internet, employ mesh routing.

http://compnetworking.about.com/cs/lanvlanwan/g/bldef_wan.htm


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Fig. 5. Mesh Topology

LAN - Local Area Network

A LAN connects network devices over a relatively short distance. A networked office building,

school, or home usually contains a single LAN, though sometimes one building will contain a

few small LANs (perhaps one per room), and occasionally a LAN will span a group of nearby

buildings. In TCP/IP networking, a LAN is often but not always implemented as a single IP

subnet.

In addition to operating in a limited space, LANs are also typically owned, controlled, and

managed by a single person or organization. They also tend to use certain connectivity

technologies, primarily Ethernet and Token Ring.

WAN - Wide Area Network

As the term implies, a WAN spans a large physical distance. The Internet is the largest WAN,

spanning the Earth.

A WAN is a geographically-dispersed collection of LANs. A network device called a router

connects LANs to a WAN. In IP networking, the router maintains both a LAN address and a

WAN address.

A WAN differs from a LAN in several important ways. Most WANs (like the Internet) are not

owned by any one organization but rather exist under collective or distributed ownership and

management. WANs tend to use technology like ATM, Frame Relay and X.25 for connectivity

over the longer distances.

LAN, WAN and Home Networking

Residences typically employ one LAN and connect to the Internet WAN via an Internet Service

Provider (ISP) using a broadband modem. The ISP provides a WAN IP address to the modem,

and all of the computers on the home network use LAN (so-called private) IP addresses. All

http://compnetworking.about.com/cs/lanvlanwan/g/bldef_lan.htm

http://compnetworking.about.com/od/tcpip/

http://compnetworking.about.com/od/workingwithipaddresses/g/bldef_subnet.htm

http://compnetworking.about.com/cs/ethernet1/g/bldef_ethernet.htm

http://compnetworking.about.com/od/networkprotocols/g/token-ring-networks.htm

http://compnetworking.about.com/cs/lanvlanwan/g/bldef_wan.htm

http://compnetworking.about.com/cs/routers/g/bldef_router.htm

http://compnetworking.about.com/od/networkprotocols/g/bldef_atm.htm

http://compnetworking.about.com/od/networkprotocols/g/framerelay.htm

http://compnetworking.about.com/cs/design/g/bldef_x25.htm

http://compnetworking.about.com/od/internetaccessbestuses/g/bldef_isp.htm

http://compnetworking.about.com/od/internetaccessbestuses/g/bldef_isp.htm

http://compnetworking.about.com/od/broadband/g/bldefcablemodem.htm

http://compnetworking.about.com/library/glossary/bldef-ipaddress.htm


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computers on the home LAN can communicate directly with each other but must go through a

central gateway, typically a broadband router, to reach the ISP.

Other Types of Area Networks

While LAN and WAN are by far the most popular network types mentioned, you may also

commonly see references to these others:

Wireless Local Area Network - a LAN based on WiFi wireless network technology

Metropolitan Area Network - a network spanning a physical area larger than a LAN but

smaller than a WAN, such as a city. A MAN is typically owned an operated by a single

entity such as a government body or large corporation.

Campus Area Network - a network spanning multiple LANs but smaller than a MAN,

such as on a university or local business campus.

Storage Area Network - connects servers to data storage devices through a technology

like Fibre Channel.

System Area Network - links high-performance computers with high-speed connections

in a cluster configuration. Also known as Cluster Area Network.

10.2 To make an Internet connection

1. Open Network Connections.

2. Under Network Tasks, click Create a new connection, and then click Next.

3. Click Connect to the Internet, and then click Next.

4. Choose one of the following:

o If you already have an account with an Internet service provider (ISP), click Set up

my connection manually and then click Next.

o If you have a CD from an ISP, click Use the CD I got from an ISP and then click

Next.

o If you do not have an Internet account, click Choose from a list of Internet service

providers (ISPs) and then click Next.

5. From your choice above, click one of the following:

� Set up my connection manually

o If you are connecting to your ISP using a standard 28.8 Kbps, 56 Kbps, or ISDN

modem, click Connect using a dial-up modem, click Next, and follow the

instructions in the wizard.

http://compnetworking.about.com/cs/dslcablerouters/g/bldef_bbrouter.htm

http://compnetworking.about.com/cs/wireless80211/g/bldef_wifi.htm

http://compnetworking.about.com/cs/fibrechannel/g/bldef_fibrechan.htm


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o If your DSL or cable modem ISP connection requires a user name and

password, click Connect using a broadband connection that requires a

user name and password, click Next, and then follow the instructions in the

wizard.

o If your DSL or cable modem ISP connection is always on and does not require

you to type a user name and password, click Connect using a broadband

connection that is always on, click Next, and then click Finish.

� Use the CD I got from an ISP

o Click Next, and then click Finish. Insert the CD provided by your ISP and

follow the instructions.

� Choose from a list of Internet service providers (ISPs)

o To create an Internet account using MSN Explorer, click Get online with MSN,

and then click Finish. Follow the instructions in MSN Explorer.

o To choose an ISP, click Select from a list of ISPs, click Finish, and then

double-click Refer me to more Internet service providers. Follow the

instructions in the wizard.

10.3 Procedure:

• To open Network Connections, click Start, point to Settings, click Control Panel, and

then double-click Network Connections.

• If your DSL or cable modem is always connected and your ISP does not require a user

name and password, you do not need to run the New Connection Wizard. No additional

configuration is required for your broadband connection.

• Before you create an Internet connection, check with your Internet service provider (ISP) to

verify the required connection settings. A connection to your ISP may require one or

more of the following settings:

o A specific IP address.

o DNS addresses and domain names.

o POP3 settings for incoming e-mail.

o SMTP settings for outgoing e-mail.


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10.3.1 To configure TCP/IP settings

1. Open Network Connections.

2. Click the connection you want to configure, and then, under Network Tasks, click

Change settings of this connection.

3. Do one of the following:

o If the connection is a local area connection, on the General tab, under This

connection, uses the following items, click Internet Protocol (TCP/IP), and

then click Properties.

o If this is a dial-up, VPN, or incoming connection, click the Networking tab. In This

connection uses the following items, click Internet Protocol (TCP/IP), and

then click Properties.

1. Do one of the following:

o If you want IP settings to be assigned automatically, click Obtain an IP address

automatically, and then click OK.

o If you want to specify an IP address or a DNS server address, do the following:

� Click Use the following IP address, and in IP address, type the IP

address.

� Click Use the following DNS server addresses, and in Preferred DNS

server and Alternate DNS server, type the addresses of the primary and

secondary DNS servers.

2. To configure DNS, WINS, and IP Settings, click Advanced.

10.3.2 Procedure to open Network connections

• To open Network Connections, click Start, point to Settings, click Control Panel, and

then double-click Network Connections.

• You should use automated IP settings (DHCP) whenever possible, for the following

reasons:

o DHCP is enabled by default.

o If your location changes, you do not have to modify your IP settings.


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o Automated IP settings are used for all connections, and they eliminate the need to

configure settings such as DNS, WINS, and so on.

10.4 TCP/IP ADDRESSING:

Every IP address can be broken down into 2 parts, the Network ID (netid) and the Host ID

(hostid).

Network id: identifies the network to which a device is attached.

Host id: The host portion of an IP address identifies the specific device on that

network

All hosts on the same network must have the same netid. Each of these hosts must have a hostid

that is unique in relation to the netid. IP addresses are divided into 4 octets with each having a

maximum value of 255. We view IP addresses in dotted decimal notation such as 124.35.62.181,

but it is actually utilized as binary data so one must be able to convert addresses back and forth.

When converting binary data to decimal, a "0" is equal to 0. "1" is equal to the number that corresponds to

the field it is in. For example, the number 213 would be 11010101 in binary notation.

This is calculated as follows: 128+64+0+16+0+4+0+1=213. Remember that this only represents 1 octet

of 8 bits, while a full IP address is 32 bits made up of 4 octets. This being true, the IP address

213.128.68.130 would look like:

11010101 10000000 01000100 10000010.

IP Address Classes:

• Class A.

When written in a binary format, the first (leftmost) bit of a Class A address is always 0.

An easy way to recognize whether a device is part of a Class A network is to look at the

first octet of its IP address, which will range from 0-126. (127 reserved for loopback and

diagnostics.) 224 - 2 = 16,777,214, possible IP addresses to devices that are attached to

its network.

• Class B.

The first 2 bits of a Class B address are always 10. Class B IP addresses always have

values ranging from 128 to 191 in their first octet. 216 - 2= 65,534 possible IP addresses

to devices that are attached to its network.


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• Class C.

The first 3 bits of a Class C address are always 110. Class C IP addresses always have

values ranging from 192 to 223 in their first octet. 28 -2 = 254 possible IP addresses to

devices that are attached to its network.

• Other Classes.

In addition to the three most popular classes, there are two additional classes, class D and

class E. Class D addresses have their leading four bits set to 1110 and are used to support

IP Multicasting. Class E addresses have their leading five bits set to 11110 and are

reserved for future use.

The formats used for IP address are shown below:

Fig. 7. Format of IP address

The IP address 0.0.0.0 is used by hosts when they are being booted but is not used

afterwards.

10.5 Accessing Internet and Email

Email:

• A Electronic mail, abbreviated e-mail or email is a method of composing, sending and

receiving messages over electronic communication systems.

• Quickly delivered in seconds or minutes (if without problem).

• What you need is

� The E-mail address of the recipient.


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� user@host

� [email protected]

• “yahoo.com" is the domain name of the mail server, which handles the recipient's mail.

• “john" is the user name of the recipient.

• User name and hostname are separated by "@".

• Carbon Copy Section

� Send a message to more than one person; all the recipients will see the list of email

addresses.

• Blind Carbon Copy Section

� The recipients won’t see others’ addresses.

� When email is sent to a large group of people who don’t know each other.

Email Services:

• Web Mail

• POP

• IMAP

POP:

• Don’t have to know the name of your machine

• POP mail server is installed on a computer always ON

• Use Windows interface to read email

• The email at the mail server is popped to your local machine

IMAP:

• Internet Message Access Protocol

• Permits a "client" email program to access remote message stores as if they were local

• No need to transfer messages or files back and forth between computers

SPAM:

• SPAM is flooding the Internet with many copies of the same message

� Force to send message to people

� Junk electronic mail.

• Why cause problem?

� Cost-shifting – very cheap to send thousands of emails


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� Fraud – not an advertisement subject

� Waste of others’ resources – stealing bandwidth

� Displacement of Normal Email–destroy the usefulness and effectiveness of email

� Ethics problem

.

10.6 How to configure Internet Explorer automatic download prompts

on your Windows XP:

Beginning with Windows XP Service Pack 2 (SP2), a new visual feature named the

Information Bar is added to Internet Explorer. You may notice that the Information Bar

alerts you to files that are blocked from being downloaded when you visit a Web site. This

article describes how to configure these automatic download prompts.

Pop-up Blockers

Pop-up windows can interrupt what you're doing, but Toolbar's Pop-up blocker blocks most

unwanted pop-ups from ever becoming a nuisance while still allowing the ones you do want to

open to open. Say that three times fast.

Enable or disable the Pop-up blocker

1. Click Toolbar's wrench icon.

2. On the Tools tab, select (or deselect) the 'Pop-up blocker' checkbox.

3. Click Save.

Allow pop-ups

To allow pop-ups, just click Toolbar's Pop-up blocker button. The button's icon should change

from 'Pop- ups blocked' to 'Pop-ups allowed' . Once you allow pop-ups on a specific

website, Pop-up blocker adds the website to an 'Allowed sites' whitelist.

View the 'Allowed sites' list

1. Click Toolbar's wrench icon.

2. On the Tools tab, click the Edit link next to the 'Pop-up blocker' checkbox.

If you're still unable to open pop-ups after clicking the Pop-up blocker button, check that IE and

your security software aren't preventing it from opening.


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Reset the Pop-up blocker counter

Click the Pop-up blocker button's drop-down menu, then select Reset count.

Block Pop-up Windows with Internet Explorer

Many legitimate advertisers on the Internet use windows that pop up in the middle of your screen

to display a message. They might also open when you click a link or button on a Web site, and

they might open either over or under the window you wish to view.

Some pop-ups are helpful. For example, if you click an image to see a larger version, it might

open in a pop-up window. Unfortunately, some pop-up windows can contain inappropriate

content or can be a way for you to accidentally download dangerous software (called spyware or

adware) onto your computer.

With Windows XP Service Pack 2 (SP2) Internet Explorer allows you to prevent most pop-up

windows from appearing over pages you want to view while you're using the Internet.

Using Pop-up Blocker

When you install SP2, Pop-up Blocker is turned on in Internet Explorer and set to the medium

setting, which means it will block most automatic pop-ups. The default settings for the pop-up

blocker allow you to see pop-ups that are opened when you click a link or button on a Web site.

Pop-up Blocker will also play a sound and show the Information Bar when a pop-up is blocked.

You can adjust these settings so that Pop-up Blocker works the way you want it to.

To change Pop-up Blocker settings

• Open Internet Explorer.

• On the Tools menu, point to Pop-up Blocker, and then click Pop-up Blocker Settings.

Internet Explorer Tools menu

If you want to see pop-up windows from a specific Web site, type the address (or URL) of the

site in the Address of Web site to allow box, and then click Add.


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Pop-up Blocker Settings window

Tip To temporarily allow a site to display pop-ups, click the Information Bar when it notifies

you that a pop-up has been blocked. Then click Temporarily Allow Pop-ups.

To block pop-ups even if they are launched when you click a link or button on a Web site:

1. Open Internet Explorer.

2. On the Tools menu, point to Pop-up Blocker, and then click Pop-up Blocker Settings.

3. Select the High setting in the box near the bottom of the dialog box.

Note If you want to see pop-ups that are blocked when you have this setting turned on, hold

down the CTRL key while the window opens.

Troubleshooting Pop-Up Blocker

If you've installed SP2 and you still see pop-ups in Internet Explorer, try the possible solutions

below.

� Make sure Pop-up Blocker is turned on: Pop-up Blocker is turned on by default, but

someone may have turned it off.


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To turn on Pop-up Blocker

1. On the Tools menu, point to Pop-up Blocker.

2. Click Turn on Pop-up Blocker.

• Rid your system of spyware: If you get similar pop-up windows no matter what sites

you visit or even if you're not on the Web at all, you could have spyware, adware, or

other software on your computer that's launching pop-ups. To stop these pop-ups, you

will have to identify the software, then remove it or change its settings to stop it from

launching pop-ups.

• Some windows are not blocked: Pop-up Blocker is smart enough to not block pop-up

windows that you open deliberately by clicking a link—for example, if you were on a

travel reservation site and you clicked a link to open a pop-up window containing

your confirmation details, this pop-up window would not be blocked because you

opened it intentionally. Also, Pop-up Blocker will not block some pop-ups with

certain types of animated content or pop-ups from

10.7 Wi-Fi configuration

(To Access WiFi Service Laptop/Computer should be Wireless Enabled)

1. Enter IP 192.168.1.1, in Internet Explorer after connecting the router as before(As in ADSL

Router without wifi capability)

2. Enter User Name Password as before(As in ADSL Router without wifi capability): i.e. admin,

admin

3. Click Tab Interface Setup shown below:

a) Click Internet, you will find page as given below:


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Fig 8:Interface setup

Configure PVCs, Enter Username & Password as earlier(As in ADSL Router without wifi

capability), and Click save button.

b) To configure Wireless setting Click Wireless Tab and you will get window as given

below:

Fig 9: configuration window


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* Activate Access Port radio button (WiFi would not work without it)

* Type your SSID.

* You can Configure Channel Id.

* Select Authentication type by clicking combo box and enter KEY in required format.

You can filter/allow Mac address by activating wireless MAC address filter as desired by

clicking Activated tab. You have to enter the mac address of your WIFI card installed in

your laptop/computer. Upto 8 MAC can be allowed or denied.

Click Save Button.

As below one USER is allowed to access the WiFi Service from this Access point. i. e.

00:14:A4:19:74:8C. If you enter WiFi Card MAC addresses of other Laptops/Computers

(Maximum 8 Laptops/Computers are allowed)

Fig 10:Interface setup

Click Save Button.


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C) To configure LAN(Local Area Network) settings like DNS, DHCP Click LAN TAB as shown below

Click Save Button.

IMPORTANT:

KEY POINT to prevent misuse of WiFi Facility by unauthorized user, ALWAYS USE

Security feature of WiFi router given above and repeated below again:

1. SSID The SSID is a unique name to identify the ADSL Router in the wireless LAN.

Wireless clients associating to the ADSL Router must have the same SSID.

Broadcast SSID Select No to hide the SSID such that a station can not obtain the SSID

through passive scanning. Select Yes to make the SSID visible so a station can obtain the

SSID through passive scanning.

2. Wireless LAN :: WEP

WEP (Wired Equivalent Privacy) encrypts data frames before transmitting over the

wireless network. Select Disable to allow all wireless computers to communicate with

the access points without any data encryption. Select 64-bit WEP or 128-bit WEP to use

data encryption.

3. Key#1~Key#4 The WEP keys are used to encrypt data. Both the ADSL Router and the

wireless clients must use the same WEP key for data transmission. If you chose 64-bit


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WEP, then enter any 5 Characters each key (1-4). If you chose 128-bit WEP, then enter

13 characters for each key (1-4).The values must be set up exactly the same on the

Access Points as they are on the wireless client stations. The same value must be assigned

to Key 1 on both the access point (your ADSL Router) and the client adapters, the same

value must be assigned to Key 2 on both the access point and the client stations and so

on, for all four WEP keys.

Wireless LAN :: WPA-PSK

Wi-Fi Protected Access, pre-shared key. Encrypts data frames before transmitting over

the wireless network.

Pre-shared Key The Pre-shared Key are used to encrypt data. Both the ADSL Router and

the wireless clients must use the same WPA-PSK key for data transmission. Key Length

8 to 64 characters.

4. Wireless LAN :: MAC Filter

You can allow or deny a list of MAC addresses associated with the wireless stations

access to the ADSL Router.

Status Use the drop down list box to enable or disable MAC address filtering.

Action Select Deny Association to block access to the router, MAC addresses not listed

will be allowed to access the router. Select Allow Association to permit access to the

router, MAC addresses not listed will be denied access to the router.

NOTE: You Should always use WiFi Facility with Activating the Security features

highlighted above.

internet & computer security exercise - 10 · it workshop lab manual 180 approved by :...

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