Introduction to Computing Sciences Lecture 5: Internet PDF

Introduction to Computing Sciences Lecture 5: Internet Hamisu Ismail AHMAD Nile University of Nigeria, Abuja Faculty of Computing Department of Cyber Security © Asim Balarabe Yazid Summary of last lecture  Network and its classification  Topology (star, bus, circle)...

Introduction to Computing Sciences Lecture 5: Internet Hamisu Ismail AHMAD Nile University of Nigeria, Abuja Faculty of Computing Department of Cyber Security © Asim Balarabe Yazid Summary of last lecture  Network and its classification  Topology (star, bus, circle)  Open and closed network  Scale (LAN, MAN, WAN)  Network protocol  Token protocol, carrier sense/multiple access collision detection  Communication over a network  Repeater, switch, bridge and router  Inter-process communication  Client/server and peer-to-peer communication © Asim Balarabe Yazid 2 Content  The Internet and Its architecture  Internet application  Network security © Asim Balarabe Yazid 3 The Internet  The Internet: one internet spanning the world  Research sponsored by US government, started by Defense Advanced Research Agency (DARPA) in 1960s later shifted to academic research  How to connect computers in such a way that will not be disrupted by local disaster?  Today involves millions of machines  WAN + MAN + LAN = Internet © Asim Balarabe Yazid 4 Internet architecture  The Internet is a collection of domains  Each domain is a network or a set of inter-connected networks controlled by a single organization  Domains must be registered through (ICANN) Internet Corporation for Assigned Names & Numbers © Asim Balarabe Yazid 5 Strategy of connecting to Internet  To simplify the process of connecting to the Internet, numerous companies, called Internet service providers ( I S P ) , allow customers to connect their domains to the Internet via the ISP's equipment or to become a part of a domain already established by the ISP  A gateway is a router connecting a domain to the rest of the Internet (referred to as the cloud) © Asim Balarabe Yazid 6 Internet addressing  Each machine on a network must have a unique address: for the Internet, this is called the Internet Protocol (IP) address  For IPv4, an IP address is a 32-bit identifier for a machine  For IPv6, an IP address is 128 bits  IP address is often written in dotted decimal notation  Example of IP address  IPv4: 216.58.216.164  IPv6: 2607:f8b0:4005:805::200e © Asim Balarabe Yazid 7 Classes of IP address © Asim Balarabe Yazid 8 Internet textural addressing  IP addresses are difficult for human to remember  Each IP may have an equivalent mnemonic address, which is composed of a domain name and a host name (e.g. www.nileuniversity.edu.ng)  Domain name is the part assigned by a registrar  Top level domain (TLD) is the classification of domain owner (for example,.com and.edu)  A domain name server (DNS) on the network translates the mnemonic addresses to binary IP addresses © Asim Balarabe Yazid 9 Internet applications  Electronic mail (e-mail)  File Transfer Protocol (FTP)  Telnet and Secure Shell  Another example? © Asim Balarabe Yazid 10 World wide web (www)  The WWW application model is a model of servers spreading hypertext documents over the Internet  A web site is a server hosting all hypertext documents controlled by one organization or individual  Hypertext Markup Language HTML is the most popular language of hypertext documents © Asim Balarabe Yazid 11 HTML and its function  HTML Page is a with a plain text and images  Allow you to add the following to you web page using a tab  Text  Image  Paragraph  Table  Form  Links, etc  HTML page must be save with.html extension zxzxzzxxxxxxxx © Asim Balarabe Yazid 12 Web page vs website Web page Website © Asim Balarabe Yazid 13 HTML file format  Entire document is printable characters  Contains tags to control display, links to other documents (or contents) © Asim Balarabe Yazid 14 CSS and its function HTML Static page CSS zxzxzzxxxxxxxx © Asim Balarabe Yazid 15 HTML VS CSS Languages for static vs dynamic WEB PROGRAMMING zxzxzzxxxxxxxx PHP JS zxzxzzxxxxxxxx MySQL zxzxzzxxxxxxxx © Asim Balarabe Yazid 18 Example of static vs dynamic  When new pages links are added manually  Web pages they appear like the following files:  MS word file.doc  Digital image files.png,.jpg Static  When new pages links are added automatically.  Content changes in respond to a users events.  A database driven website. zxzxzzxxxxxxxx Dynamic © Asim Balarabe Yazid 19 MySQL and its functions Database Relational database MySQL  MySQL will allow you to:  Create database  Manage data held in RDBMS  Insert  Update  Delete  Search 20 © Asim Balarabe Yazid What can PHP do for you?  HTML embedded scripting language primarily used for dynamic website  PHP will allow you to:  Create database driven project (communicate with DB) PHP Server Database More precisely in lecture 6! 21 © Asim Balarabe Yazid Web development tools  Text editor  Notepad  Visual Studio Code  Sublime Text  Server  MIIS  XAMPP  WAMP  Browser  Chrome  Firefox  Internet explorer 22 © Asim Balarabe Yazid World wide web implementation  Web server  provides access to documents on its machine as requested  Browser  allows user to access web pages  Hypertext Transfer Protocol (HTTP)  communication protocol used by browsers and web servers  Uniform Resource Locator (URL)  unique address of a document on the web © Asim Balarabe Yazid 23 Network security  Integrity of machine exposed to internet can be attacked by the following Malwares:  Viruses and worms  Trojan horses  Spywares (sniffing), etc.  Defense techniques  Firewall  Anti-virus and anti-spyware tools © Asim Balarabe Yazid 24  Trojan Horse The most famous war in history, The Trojan War, took place around the year 1300 BCE. During this war, the impenetrable Troy fell before Greece, after 10 years of siege. When the conquering Greeks were close to victory, Achilles, their most famous warrior, was killed. The path to victory began when Odysseus, who was being instructed by Athena (the goddess who gave the olive tree to humanity), conceived the plan of building a giant horse made of olive wood and hiding his best warriors inside. The ever famous Trojan Horse was built in the Anatolian region, where the olive tree originates from. With the wood and help from Athena, the fabulous plan was devised that ended up piercing the  Computer Trojan Horse A Trojan is another type of malware named after the wooden horse that the Greeks used to infiltrate Troy. It is a harmful piece of software that looks legitimate. Users are typically tricked into loading and executing it on their systems. After it is activated, it can achieve any number of attacks on the host, from irritating the user (popping up windows or changing desktops) to damaging the host (deleting files, stealing data, or activating and spreading other malware, such as viruses). Trojans are also known to create backdoors to give malicious users access to the system. Unlike viruses and worms, Trojans do not reproduce by infecting other files nor do they self-replicate. Trojans must spread through user interaction such as opening an email attachment or downloading and running a file from the Internet.  Computer Virus & Worms A computer virus is a type of malware that propagates by inserting a copy of itself into and becoming part of another program. It spreads from one computer to another, leaving infections as it travels. Viruses can range in severity from causing mildly annoying effects to damaging data or software and causing denial-of-service (DoS) conditions. Computer worms are similar to viruses in that they replicate functional copies of themselves and can cause the same type of damage. In contrast to viruses, which require the spreading of an infected host file, worms are standalone software and do not require a host program or human help to propagate. To spread, worms either exploit a vulnerability on the target system or use some kind of social engineering to trick users into executing them.  Spyware Sniffing is a process of monitoring and capturing all data packets passing through given network. Sniffers are used by network/system administrator to monitor and troubleshoot network traffic. Attackers use sniffers to capture data packets containing sensitive information such as password, account information etc. Privacy in communication  In the old days, most data send over the Internet were unprotected  A network sniffer can be used to collect your private data  Today, encryptions are used to protect your privacy  Secure versions of network protocols such as FTPS, HTTPS, are used to transmit data with encryption  You can also encrypt data by yourself © Asim Balarabe Yazid 29 Summary  The Internet and Its architecture  Internet application  Email, FTP, Telnet and secure shell  WWW development and implementation  HTML, CSS, MySQL, PHP  Network security (Attacks and Defenses)  Privacy in communication (encryption and decryption) © Asim Balarabe Yazid 30 Additional reading  Goldfarb, C. F. and P. Prescod. The XML Handbook, 5th ed. Upper Saddle River, NJ: Prentice-Hall, 2004.  Halsal, F. Computer Networking and the Internet, Boston, MA: Addison-Wesley, 2005.  Kurose, J. F. and K. W Ross. Computer Networking; A Tbp Down Approach Featuring the Internet, 3rd ed. Boston, MA: Addison- Wesley, 2003.  Peterson, L. L. and B. S. Davie. Computer Networks: A Systems Approach, 3rd ed. San Francisco: Morgan Kaufmann, 2003.  Stallings, W. Cryptography and Network Security, 4th ed. Upper Saddle River, NJ: Prentice-Hall, 2006. © Asim Balarabe Yazid 31 Glimpse of next class  Concept of algorithm  Representation of algorithm  Algorithms discovery  Structure of algorithm  Efficiency and correctness of algorithms © Asim Balarabe Yazid 32 Lecture 05 Ends Question??? Thank you for coming. © Asim Balarabe Yazid 33