Computer Networks

1. Computer Networks

2. Types of Wireless Network Attacks - 1 • Insertion attacks: When a wireless device connects to an access point without authorization • Interception /monitoring of wireless traffic: The network traffic across a WLAN is intercepted and monitored without authorization. • Mis-configuration: Many access points ship in an unsecured configuration

3. WLAN Security • WEP: Wired Equivalent Privacy • WPA: Wi-Fi Protected Access • WPA2: Best protection for home WLAN.

4. WEP: Wired Equivalent Privacy • Purpose: • Protect wireless network from eavesdropping. • Prevent unauthorized access to the network • How Does It Work • A secret key between laptop and access point • The secret key to encrypt packets • Length of Key • 64-bit encryption • 128-bit encryption

5. WPA: Wi-Fi Protected Access • Two types of WPA • WPA-PSK (WPA Personal) - Home &Small Offices • WPA-RADIUS (WPA Enterprise) – Large Organizations • WPA-PSK: Pre-Shared Key • Extra-strong encryption • Encryption keys are automatically changed • after a specified period of time • after a specified number of packets • Implements a subset of IEEE 802.11i.

6. WPA2: Wi-Fi Protected Access • WPA2: Best protection for home WLAN. • Fully compatible with IEEE 802.11i security standard. • Stronger encryption protocol • Not all wireless cards and access points support • WPA2 certification is mandatory for all new devices wishing to be Wi-Fi certified.

7. The Internet

8. What is the Internet? • The Internet involves millions of computers, connected in complex ways to a maze of local and regional networks

9. Origins of the Internet • 1969 • Department of Defense established experimental network connecting 4 research computers (UCLA, Stanford Research Institute (SRI) , UC@Santa Barbara and U. of Utah. • Called ARPANET • 1980s National Science Foundation involved • Only scientific, research and academic institutions (no commercial traffic)

10. Other Developments… • 1989 - E-mail connectivity thru CompuServe and MCI Mail • 1991 – move towards private sector • National Access Points (NAPs) • Internet Service Providers (ISPs) • Communication coordinated through national and international organizations (standards)

11. Who Owns the Internet? • No one company or country can be considered as owner of Internet • Ownership shared among various entities • Coordination: • Internet Society (ISOC) • Internet Engineering Task Force (IETF) • Internet Architecture Board (IAB) • In the US – • ICANN – Internet names and port numbers (Internet Corporation for Assigned Names and Numbers)

12. Cost ($$$$)… • Revenue is required to offset expenses • Servers, routers, communication lines, etc. • Costs must be covered by users • Companies, organizations and individuals • AOL – subscribers charges monthly fee

13. Internet Address • Domain Name • Logical name for computing system www.scranton.edu • Top-Level Domain (suffix) • ICANN • IP Number • 32-bit address (4 part decimal #) • ARIN (American Registry for Internet Numbers)/ RIPE / APNIC • 132.161.33.60

14. Internet Address… • Ethernet Address • 48-bit address built into machine or Ethernet board • Refers to specific board in a local computer

15. Addressing • Domain Name Server (local) • Network Information Server (wider area) • Maintain databases with domain names and IP numbers in binary format Domain Name  IP Number (logical)  Ethernet Address (physical)

16. Laptops • Static IP address • Specified manually and entered into network tables • Dynamic IP address • Dynamic Host Configuration Protocol (DHCP) • Ask network for an IP address when you turn it on (from a pool of available addresses) • IP address changes each time computer is used

17. Web Browsers • Internet Explorer, Mozilla, Netscape Navigator, Firefox • System of communicating Web documents • Hypertext Transfer Protocol (HTTP) • Formatting instructions called: • HTML (Hypertext Markup Language)

18. How info is transmitted? • Uniform Resource Locator (URL) http://www.cs.uofs.edu/~bi/2005f-html/cil102/chap-sum.html Hypertext Transfer Protocol Directory path Domain name of the Web server Web page

19. What info is transmitted? • Each time you access the Web, the browser sends the following to the Web server • The IP address of your machine • Often it can identify your town or ISP • The web server’s IP address • The OS you use on your machine • The browser you use • Goto http://www.cs.grinnell.edu/~walker/fluency-book/web-info.php to see how much info is sent to the Web server

20. What are Cookies? • Have you ever gone to a website that seemed to remember you? • Websites use cookies to store info about you on your own computer • When you visit such a website, it stores info as cookies (that appear as files) on your computer • Next you visit the same website, your browser sends over all the cookies stored by that website • What info is stored in cookies? • In theory, anything the website wants to • Normally, it is about how you used the website • A website could store your id, password, etc in cookies if it has that info.

21. What are Cookies? • The positive side of cookies • A Web server can use cookies to streamline and personalize your interactions with it • A browser is supposed to send cookies only to the Web server who stored them. • The negative side of cookies • Companies may use cookies to store info for other purposes without your permission • There are ways for a Web server to get cookies that were stored by other Web servers.

22. What defenses against Cookies • For the website you visit, especially, those websites you need to register, check: • How will the company use the info you supply? • Will the company share info with others? • Can you limit access of other to this info? • What protections are in place to keep this info?

23. What defenses against Cookies • If you use a computer at work or school, cookies would be stored on school or company’s computer: • System administrators or managers may read your cookies files • View your organization’s privacy policy • Technicians may inadvertently access your cookies, when your computer was sent for repair, for example. • Best way to protect yourself, delete cookies. • Almost every browser has a function you can use to delete cookies.

24. How secure is info during transmission • When you use the Internet, all data you put on the network is visible to computers on the same Ethernet, as discussed in the Network chapter. • When your data need to be passed from one segment to another segment of the network, the intermediate computers can read your data. • Thus, info is not secure at all when transmitted on the Internet.

25. How secure is info during transmission • One way to protect yourself is encrypt info that you want to be confidential • When data is encrypted, it can still be copied or intercepted by other computers, however, they would not know what it means. • When a good encryption is used, it may take years, decades to break the code • When shopping (or passing private info) on the Web, make sure the website uses HTTPS protocol. • HTTPS: Secure HTTP, which asks the browser to encrypt the data before it is transmitted and the server decrypts data upon receiving.

26. Security

27. Data Availability • Data in memory is volatile. • Data in storage is non-volatile so it is always available • As long as it isn’t trashed accidentally or deliberately. • So, when using software (Word, etc.) save often.

28. Data Availability • BACK UP IMPORTANT DATA • Often • Specifically what should YOU do with your data. • At least once per semester, back up your entire computer if it is at all convenient. • I use a removable hard disk • They are currently cheap

29. Data Security • Secure data is data that is difficult for OTHERS to access. • There are two basic methods of securing data: • Password systems • Encryption

30. Password Systems • Username and Password – Good systems will not tell you which one is wrong if one of them is. • Usernames are often given to you so you have no choice as to what to use. • Most people choose their own passwords.

31. Choosing Passwords • Make it long. • Use both letters and digits, maybe even special symbols • Use upper and lower case. • Example: dsitBtitw5 (dr sidbury is the best teacher in the world 5) • Example: P=2*(L+w)

32. Cryptography/Encryption • Ebubjtfodpefetpuibujuepfto’umpplopsnbm. • Data is encoded so that it doesn’t look normal.

33. What are viruses? • Unwanted and unanticipated programs • May damage a computer or degrade its performance • Viruses may appear: • As an email attachment • In another program • In user data files (MS Word Macros) • On disk in a place that is routinely activated. • A virus cannot be spread without a human action • Worms • Similar to viruses • Have capability to travel without any human action • e.g., send a copy of itself to everyone in your email address book, then send to everyone in the receiver’s addr book

34. How to detect viruses? • Anti-virus programs compare each file against known viruses • A computer may be set up in such a way that no disk files can be accessed until virus scanning has been completed. • A new virus may not be known by the anti-virus program until the virus information is available to the anti-virus program • Be proactive in getting information of new viruses for the anti-virus program

35. How to protect yourself? • Be sure anti-virus software is running on your computer and keep the virus info up to date • Do not execute (open) any program (file) downloaded from the Internet without first having it scanned for viruses. • Be cautious before allowing your Web browser to run programs behind the scenes • Save all your email attachments to hard disk and scan them for viruses before open them • Do not run any macro in Word documents or Excel spreadsheets unless you know they are reliable • Install and configure firewalls if your computer is connected to the Web.

36. Spyware • Keyboard Sniffers • Wire tapping • Trojan Horses • Packet Sniffer

37. Firewalls • A firewall controls/monitors traffic from one system to another one. • The systems may be individual computers or networks. • A firewall can block unauthorized access to your computer while permitting authorized communications • Most computers which you buy have a built in firewall. You should configure them or you will not be able to use software correctly.