CSC 140: Introduction to IT

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

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

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

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

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. CIT 140: Introduction to IT

6. Example SMTP Session S: 220 www.example.com ESMTP Postfix C: HELO mydomain.com S: 250 Hello mydomain.com C: MAIL FROM: <sender@mydomain.com> S: 250 Ok C: RCPT TO: <friend@example.com> 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 CIT 140: Introduction to IT

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. CIT 140: Introduction to IT

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. CIT 140: Introduction to IT

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. CIT 140: Introduction to IT

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. CIT 140: Introduction to IT

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. CIT 140: Introduction to IT

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 <zeecat@utoledo.edu>; 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: <4.2.2.20050915030222.02c6ea30@61.221.11.71> Date: Thu, 15 Sep 2005 03:05:55 -0500 Reply-To: Bruce Xyzzy <xyzzy@COUNTERPANE.COM> From: Bruce Xyzzy <xyzzy@COUNTERPANE.COM> Subject: CRYPTO-GRAM, September 15, 2005 To: CRYPTO-GRAM-LIST@LISTSERV.MODWEST.COM Precedence: list CIT 140: Introduction to IT

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 CIT 140: Introduction to IT

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/5mjgQjcipBUL1b3uyLwAVtBLOP4nV LdIAhSzlZnyLAF8na0n7g6OSeej7aqIl3NIXCfxDsPsY6NQjSvV77j4hWEjlF/aglS6ghfju FgRr+OX8QZMI1OmR4rUJUS7xgoknalqj3HJvaOpeb3CFlNI9VGZYz6H6zuQBOWZzNB8glwpC --frontier-- CIT 140: Introduction to IT

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. CIT 140: Introduction to IT

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. CIT 140: Introduction to IT

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. CIT 140: Introduction to IT

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. CIT 140: Introduction to IT

19. E-mail Features CIT 140: Introduction to IT

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 CIT 140: Introduction to IT

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

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

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

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

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

26. pine CIT 140: Introduction to IT

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

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