1. CIT 140: Introduction to ITSlide #1 CSC 140: Introduction to IT Electronic Mail

2. CIT 140: Introduction to ITSlide #2 Topics What is E-mail? E-mail Protocols E-mail Addresses E-mail Headers UNIX e-mail Applications –mail –pine –KMail

3. CIT 140: Introduction to ITSlide #3 What is E-mail? A method of composing, sending, and receiving messages over electronic communication systems.

4. CIT 140: Introduction to ITSlide #4 E-mail Transfer Dialog

5. CIT 140: Introduction to ITSlide #5 E-mail Protocols: Sending Simple Mail Transfer Protocol (SMTP) –This dictates the format of the message in terms of an envelope, a header and a body and facilitates the movement of the message between the components of a typical e-mail transfer. Domain Name System (DNS) –This dictates the exact form of an e-mail address.

6. CIT 140: Introduction to ITSlide #6 Example SMTP Session S: 220 www.example.com ESMTP Postfix C: HELO mydomain.com S: 250 Hello mydomain.com C: MAIL FROM: S: 250 Ok C: RCPT TO: S: 250 Ok C: DATA S: 354 End data with. C: Subject: test message C: From: sender@mydomain.com C: To: friend@example.com C: C: Hello, C: This is a test. C:. S: 250 Ok: queued as 12345 C: QUIT S: 221 Bye

7. CIT 140: Introduction to ITSlide #7 E-mail Protocols: Receiving Post Office Protocol (POP) or Internet Message Access Protocol (IMAP) –Works best for offline e-mail reading from a single host computer that contains your e-mail. Multipurpose Internet Mail Extensions (MIME) –This dictates the format of multimedia files used as attachments to an e-mail message.

8. CIT 140: Introduction to ITSlide #8 History of E-mail 1965 –First e-mail on mainframe systems like CTSS. 1969 –Internet started. –First e-mail messages sent on Internet. 1978 –First spam e-mail message sent from a DEC engineer. 1981 –RFC 788 published, describing SMTP. 1983 –DNS released, allowing user@host.domain addresses.user@host.domain

9. CIT 140: Introduction to ITSlide #9 E-mail Addresses Bang Paths –utzoo!decvax!harpo!eagle!mhtsa!ihnss!ihuxp!grg –Recipient: grg –Recipient’s machine: ihuxp –Machines connected by modems at night to avoid long- distance charges. –Transmission times measured in days.

10. CIT 140: Introduction to ITSlide #10 E-mail Addresses jw@cs.nku.edu –Top level domain: edu Limited: com, edu, gov, net, org, country codes Internet Assigned Numbers Authority (IANA) ICANN controls IANA –Subdomain: nku Allocated by top-level domain administrators. –Hostname: cs Allocated by subdomain administrators. –Username: jw Allocated by hostname administrators.

11. CIT 140: Introduction to ITSlide #11 E-mail Headers To: contains e-mail address(es) of recipient(s) From: contains the e-mail address of sender. Cc: address(es) of additional recipient(s). Date: Date and time at which message was sent. Attch: lists any attachments that might accompany the message, usually in the form of external files. Subject: indicates the subject of message. Received: tracking information indicating which servers handled the message.

12. CIT 140: Introduction to ITSlide #12 Example E-mail Headers From owner-crypto-list@LISTSERV.MODWEST.COM Thu Sep 15 06:03:01 2005 Received: from mailapp0.msomt.modwest.com (mailapp0.msomt.modwest.com [216.220.25.71]) by smtp.utoledo.edu (8.14.7) with ESMTP id j8FA30407908 for ; Thu, 15 Sep 2005 06:03:00 -0400 (EDT) Received: from nat.dd-b.net (HELO rafael) (61.221.11.71) by mpls-pop-13.inet.qwest.net with SMTP; 15 Sep 2005 08:06:00 -0000 X-Sender: schneier@counterpane.com (Unverified) X-Mailer: QUALCOMM Windows Eudora Pro Version 4.2.2 Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed X-Modwest-MailScanner: Found to be clean Message-ID: Date: Thu, 15 Sep 2005 03:05:55 -0500 Reply-To: Bruce Xyzzy From: Bruce Xyzzy Subject: CRYPTO-GRAM, September 15, 2005 To: CRYPTO-GRAM-LIST@LISTSERV.MODWEST.COM Precedence: list

13. CIT 140: Introduction to ITSlide #13 Attachments E-mail historically used 7-bit ASCII. Binary files, such as images or programs, require 8 bits of data per byte. MIME –Encodes 8-bit files as 7-bit ASCII. –Stores multiple files with a single message. MIME Headers –MIME-Version: 1.0 –Content-type: text/plain –Content-transfer-encoding: base64

14. CIT 140: Introduction to ITSlide #14 MIME Message Example Content-type: multipart/mixed; boundary="frontier" MIME-version: 1.0 --frontier Content-type: text/plain This is the body of the message. --frontier Content-type: application/octet-stream Content-transfer-encoding: base64 gajwO4+n2Fy4FV3V7zD9awd7uG8/TITP/vIocxXnnf/5mjgQjcip BUL1b3uyLwAVtBLOP4nV LdIAhSzlZnyLAF8na0n7g6OSeej7aqIl3NIXCfxDsPsY6NQjSvV 77j4hWEjlF/aglS6ghfju FgRr+OX8QZMI1OmR4rUJUS7xgoknalqj3HJvaOpeb3CFlNI9V GZYz6H6zuQBOWZzNB8glwpC --frontier--

15. CIT 140: Introduction to ITSlide #15 Privacy E-mail is transmitted through several MTAs on its way from sender to recipient. –E-mail can be read on disk of mail server. –E-mail can be read in transit using a sniffer. Additional privacy issues –Your e-mail address is included in headers. –Your e-mail server is displayed in headers.

16. CIT 140: Introduction to ITSlide #16 Threats Snooping –Others reading your e-mail. Spoofing –Forging e-mail to appear to be from someone else. Identity Theft –An attacker impersonates you or someone you know by spoofing e-mail to appear to be from them. –Phishing Repudiation –Since attackers can impersonate others in e-mail, people deny sending e-mail they actually wrote. Fraud –419 scams.

17. CIT 140: Introduction to ITSlide #17 Security Measures Encrypt e-mail in transit. –SSL encryption for POP, IMAP, SMTP. –Many e-mail clients and servers support. –Also SSL encryption for webmail. Encrypt e-mail before transit –PGP and S/MIME (incompatible with each other.) –Must exchange cryptographic keys with recipient. –E-mail encrypted in storage and in transit. –Message Authentication Codes used to check if encrypted message was altered.

18. CIT 140: Introduction to ITSlide #18 UNIX E-mail Files /var/mail/username /var/spool/mail/username –A user’s e-mail messages. /var/spool/mqueue –Messages queued for sending to other hosts. /etc/mail –Mail server (MTA) configuration files. /etc/mail/aliases –MTA mailing lists.

19. CIT 140: Introduction to ITSlide #19 E-mail Features

20. CIT 140: Introduction to ITSlide #20 The UNIX mail Command Options for sending e-mail with the mail command -s A subject: line is included in the message header for all recipients -c A carbon copy is sent to address add -b A blind carbon copy is sent to address add -h A screen display of message headers is shown first -p All messages are displayed with full headers

21. CIT 140: Introduction to ITSlide #21 Graphical E-mail with KMail

22. CIT 140: Introduction to ITSlide #22 Graphical E-mail with KMail

23. CIT 140: Introduction to ITSlide #23 Graphical E-mail with KMail

24. CIT 140: Introduction to ITSlide #24 Graphical E-mail with KMail

25. CIT 140: Introduction to ITSlide #25 Graphical E-mail with KMail

26. CIT 140: Introduction to ITSlide #26 pine

27. CIT 140: Introduction to ITSlide #27 Composing E-mail with pine

28. CIT 140: Introduction to ITSlide #28 Using the pine Address Book