1. COS 125 DAY 4

2. Agenda Questions from last Class?? Today’s topics Communicating on the Internet Assignment #1 due Assignment #2 will be posted next week Quiz #1 on Feb 3, 20 M/C, 4 Short essays, One extra Credit Chap 1-28

3. Communicating on the Internet How email works How email Spam works How Newsgroup work Next week How Internet Chat and Instant Messaging Work How Internet Phone calls work

4. email Animation from www.learnthenet.com

5. How email works Most heavily used feature on the Internet Advantages Asynchronous Ubiquitous Can be made Secure (almost too secure) Disadvantage Impersonal Ubiquitous Insecure (non-confidentiality) Virus, Macros, Trojans Horses Lack of a centralized directory

6. How email works To send email You need an email account someone@somewhere.com With an email you can send Plain text HTML Attachments Email Demo from www.learnthenet.com

7. Outlook email client

8. Where is email is sent? How does your email server know where to send mail? DNS MX records Every Domain has an MX record that tells you what Mail server is responsible for that domain’s email

9. Mail to and from

10. Email end to end

11. Mailing Lists A group of people that has similar interests Each person joins the “group” which has an email address assigned group1@lists.comgroup1@lists.com When you send and email to group1@lists.com everyone that joins the group gets the email group1@lists.com Two types of Mailing lists Moderated Unmoderated Mailing List Demo from www.learnthenet.com

12. Making email secure Encryption Scramble and then descramble the message using a secret code Most encryption uses two “keys” One to scramble The other to unscramble Some only use one Encryption demo from Seidcon.com Encryption Demo from learnthenet.com

13. Public Key Encryption for Confidentiality Encrypt with Party B’s Public Key Party A Party B Decrypt with Party B’s Private Key

14. Public Key Encryption for Confidentiality Decrypt with Party A’s Private Key Party A Encrypt with Party A’s Public Key Party B

15. Getting Public keys

16. Using Encryption in email

17. LDAP White pages for computer users LDAP client <> LDAP Server Client asks for an address Server return the address Built into Windows 2000 and XP

18. How SPAM works SPAM is unsolicited Junk email Why is this done CHEAP mass marketing Junk postal mail costs at least $0.20 per mailing Spam cost around $100 per million email sent or $0.0001 per mailing

19. Tricks of the SPAMMER trade Getting email address Directories Newsgroups Pay from other spammers Build a web site to collect them Sending emails Manipulate headers to hide sending info Uses some elses email sever

20. Stopping Spammers Laws don’t work Can’t prosecute what you can’t catch Laws are tied to jurisdictions, Spammers aren’t Spam laws Special anti-spam software Spammer just get “trickyer” and by pass software Blocking places that send spam Since spammer don’t use their own mail servers you run the risk of blocking legitimate email Best practice –Get more email addresses Get an email address just for spammers me@hotmail.com Protect important emails by using sparingly One just for family & friends One just for work or school

21. Newsgroups USENET is the worlds biggest discussion forum. Collections of newsgroup of many subjects Best place to see the groups is http://groups.google.com Demo of newsgroups from Learnthenet.com Just like mailing lists newsgroup cane be Moderated Unmoderated

22. How Usenet Servers works Server replicates newsgroups to each other. Users can use any of the Usenet Servers to post and receives Postings.

23. Problems with USENET With the advent of instant messaging, MSN, AOL and Yahoo groups, blogs and other new internet inventions Usenet isn’t used but much of the Internet population Many ISP’s don’t support USENET A lot of what’s “bad” with the internet is on USENET..the equivalent of the Internet “bad part of town” Hate groups & terrorists Pornography Hackers and crackers Perverts & pedophiles Better places for discussions groups MSN groups Yahoo groups topica

24. Foe next week Read through Chapter 28 (page 176) Assignment two will be assigned Quiz 1 on Feb 3