Introduction to Cyber Security

Class	Address range
Supports
Class A	1.0.0.1 to 126.255.255.254	Supports 16 million hosts on each of 127 networks.
Class B	128.1.0.1 to 191.255.255.254	Supports 65,000 hosts on each of 16,000 networks.
Class C	192.0.1.1 to 223.255.254.254	Supports 254 hosts on each of 2 million networks
Class D	224.0.0.0 to 239.255.255.255	Reserved for multicast groups
Class E	240.0.0.0 to 254.255.255.254	Reserved for future use, or Research and Development Purposes.

IANA decentralises that task of assigning the IP addresses by allocating the large chunk of IP addresses to five Regional Internet Registries (RIRs), which are further responsible to
allocate the IP addresses in their zone. These RIRs along with their area of operations are listed below:

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  APNIC- This RIR is responsible for serving the Asia Pacific region
  
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  AfriNIC- This RIR is responsible for serving the African region
  
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  ARIN- This RIR is responsible for serving North America and several Caribbean and North Atlantic islands
  
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  LACNIC- This RIR is responsible for serving Latin America and the Caribbean, and
  
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  RIPE NCC- This RIR is responsible for serving Europe, the Middle East, and parts of Central Asia
  

For liaison and coordinating between these five RIRs, there is an organization called Number Resource Organization(NRO). These organizations are

2. DNS

Whenever we browse any website in the internet, we type name something like www.uou.ac.in and we rarely deal with IP address like 104.28.2.92 but the fact is even if we type http:\\ 104.28.2.92 in the URL, it will land us to the same webpage. The fact is we are very comfortable using and remembering the names instead of a number. Moreover, these IP address changes over time and some of the sites have multiple IP address. Also, the transfer of the data over internet is only possible using IP addresses because the routing of the packet of data sent over internet is done using IP address. There is a server called Domain Name System(DNS) which take cares of this translation job to simplify and to save us from remembering these changing IP address numbers, the DNS. Whenever you type an address like http:\\www.uou.ac.in, there is a process called DNS name resolution, takes place in the background. The computer keeps the track of recently visited sites and locally maintains a database in DNS cache. In case, the IP address of the site you have requested for is not found in the DNS cache of your local computer, then the next probable place to find it is DNS server of your Internet Service Provider(ISP). These DNS servers of ISP also maintain the cache of the recently visited pages. Just in case, the information is not found here also, the DNS server of the ISP forward the query to the root nameservers. The root name servers publish the root zone file to other DNS servers and clients on the Internet. The root zone file describes where the authoritative servers for the DNS top-level domains (TLD) are located. There are currently 13 rootname servers. They are:

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  A - VeriSign Global Registry Services
  
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  B - University of Southern California - Information Sciences Institute
  
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  C - Cogent Communications
  
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  D - University of Maryland
  
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  E - NASA Ames Research Center
  
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  F - Internet Systems Consortium, Inc.
  
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  G - U.S. DOD Network Information Center
  
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  H - U.S. Army Research Lab
  
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  I - Autonomica/NORDUnet
  
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  J - VeriSign Global Registry Services
  
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  K - RIPE NCC
  
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  L - ICANN
  
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  M - WIDE Project
  

These root nameservers directs the query to the appropriate Top-Level Domain(TLD) nameservers by reading the last part of the URL first. In our example the url was http:\\www.uou.ac.in. The last part is .in. Some of the examples of TLD name servers are

.com, .biz, .org, .us, .in, etc. These TLD nameservers acts as a switchboard and direct the query to the appropriate authoritative nameserver maintained by each domain. These authoritative nameserver maintains DNS records along with other useful information. This address record is returned back to the requesting host computer via TLD nameservers, nameservers, ISP‟s DNS server. These intermediaty server keeps the recond of this IP address in their DNS cache, so that if the same request is encountered again , they don‟t have to go through this process again. If the same URL is requested again, the DNS cache of the local host computer will return the IP address of the URL.

3. Internet Infrastructure

Internet, as the name suggests, in a network of network i.e. it is a collection of several small, medium and large networks. This clearly indicates to one fact, nobody is a single owner of the internet and it is one of the proven example of collaborative success. Now you must be surprised how such a large network which is spread across the continents can run without the any problem. Yes it is correct that to monitor such a large network, we require an international body which can frame the rules, regulation and protocols to join and use this network. Therefore, an international organization, known as “The Internet Society” was formed in 1992 to take care of such issues.
Let us now discuss, how this internet works? How the email you sent to your friend is received by your friend‟s computer located at another country/continent. When you are working in your laptop/desktop in your home without connecting to the internet, your computer is a standalone system. But, whenever you connect to the internet by dialling to your Internet Service Provider(ISP) using your modem, you become the part of the network. The ISP is the link between the internet backbone, through which the entire data route, and the user. The ISP connects to the internet backbone at Network Access Points(NAP). These NAPs are the provided by the large telecommunication companies at various regions. These large telecommunication companies connect the countries and the continents by building and maintaining the large backbone infrastructure to route data from NAP to NAP. ISPs are connected to this backbone at NAP and are responsible build and manage network locally. So when you dial internet through modem, you first become part of the local ISP, which in turn connects to the internet backbone through NAP. The data is routed through this backbone and sent to the destination NAP, where the ISP of your friend‟s network is located. As soon as your friend dials his modem to connect to the internet, the data is delivered to your friend‟s computer.

4. World Wide Web

Sometimes we interchangeably use the term internet and world wide web or simply the web, as it is popularly known as. But web is only one of the several the utilities that internet provides. Some of the popular service that internet provides other then web is e-mail, usenet, messaging service, FTP, etc. The web use HTTP protocol to communicate over internet and to exchange information. The web was developed at CERN (Europeen de Reserches Nucleaires), Switzerland) by a UK scientist Tim Berners-Lee in 1989. It consists of all the public web sites and all the devices that access the web content. WWW is an information sharing model which is developed to exchange information over the internet. There are plenty of public websites, which is a collection of web pages, available over the internet. These web- pages contain plenty of information in a form of text, videos, audio and picture format. These web pages are access using a application software called a web browser. Some of the examples of the popular web browser are: Internet explorer, Chrome, Safari, Firefox, etc.
So this was a little indroduction about internet and how it functions. Now let us discuss about cyber crime.

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