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COS 125
DAY 4
Agenda
Questions from last Class??Today’s topics
Communicating on the InternetAssignment #1 dueAssignment #2 will be posted next weekQuiz #1 on Feb 3,
20 M/C, 4 Short essays, One extra Credit Chap 1-28
Communicating on the Internet
How email worksHow email Spam worksHow Newsgroup workNext week
How Internet Chat and Instant Messaging Work
How Internet Phone calls work
Animation from www.learnthenet.com
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
How email works
To send emailYou need an email [email protected]
With an email you can sendPlain textHTMLAttachments
Email Demo from www.learnthenet.com
Outlook email client
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
Mail to and from
Email end to end
Mailing Lists
A group of people that has similar interests Each person joins the “group” which has an
email address assigned [email protected] When you send and email to
[email protected] everyone that joins the group gets the email
Two types of Mailing lists Moderated Unmoderated
Mailing List Demo from www.learnthenet.com
Making email secure
EncryptionScramble and then descramble the
message using a secret codeMost encryption uses two “keys”
One to scrambleThe other to unscramble
Some only use oneEncryption demo from Seidcon.comEncryption Demo from learnthenet.com
Public Key Encryption for Confidentiality
Encrypt withParty B’s Public Key
Party A Party B
Decrypt withParty B’s Private Key
Public Key Encryption for Confidentiality
Decrypt withParty A’s Private Key
Party A
Encrypt withParty A’s Public Key
Party B
Getting Public keys
Using Encryption in email
LDAP
White pages for computer usersLDAP client <> LDAP Server
Client asks for an addressServer return the address
Built into Windows 2000 and XP
How SPAM works
SPAM is unsolicited Junk emailWhy is this done
CHEAP mass marketingJunk postal mail costs at least $0.20 per
mailing Spam cost around $100 per million email
sent or $0.0001 per mailing
Tricks of the SPAMMER trade
Getting email addressDirectoriesNewsgroupsPay from other spammersBuild a web site to collect them
Sending emailsManipulate headers to hide sending infoUses some elses email sever
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 [email protected]
Protect important emails by using sparingly One just for family & friends One just for work or school
Newsgroups
USENET is the worlds biggest discussion forum.Collections of newsgroup of many subjectsBest place to see the groups is
http://groups.google.comDemo of newsgroups from Learnthenet.comJust like mailing lists newsgroup cane be
ModeratedUnmoderated
How Usenet Servers works
Server replicates newsgroups to each other.
Users can use any of the UsenetServers to post and receives Postings.
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
Foe next week
Read through Chapter 28 (page 176)Assignment two will be assignedQuiz 1 on Feb 3
