vault backup: 2023-04-18 15:13:52

content/notes/14-mail-servers.md

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+---
+title: "14-mail-servers"
+tags: 
+- lecture
+- cosc301
+---
+
+
+What is an email? 
+- A formatted file in ASCII code 
+- Consists of 
+	- Envelope 
+	- Header 
+	- Body
+
+![](https://i.imgur.com/F5e7LZs.png)
+
+Components in Email Architecture 
+- User Agent (UA) 
+	- For users to compose, send, and browse emails 
+	- pine, Mail, ThunderBird 
+- Mail Transport Agent (MTA) 
+	- Emails are handed to it for delivery 
+	- sendmail, exim 
+- Mail Access Agent (MAA) 
+	- Retrieve message from mailbox
+
+![Email Architecture](https://i.imgur.com/EtIiCDZ.png)
+
+> [!INFO] could be delivered through many proxies
+
+Email Protocols 
+- SMTP (Simple Mail Transfer Protocol) 
+	- Email delivery protocol between two MTAs 
+	- Used twice: between the sender and the sender’s mail server and between the two mail servers 
+- Mail fetching protocols 
+	- Between the receiver and its mail server 
+	- Post Office Protocol (POP): simple but limited in functionality 
+	- Internet Mail Access Protocol (IMAP): more features, more powerful and more complex. 
+		- Can check the e-mail header prior to downloading 
+		- Can search the contents for a specific string prior to downloading 
+		- Can partially download email
+
+> [!INFO] STMP sender - server, server to server
+> POP simple and limited, STMP more features + more config required
+
+SMTP example SMTP example 
+- S: 220 smtp.example.com ESMTP Postfix 
+- C: HELO relay.example.org 
+- S: 250 Hello relay.example.org, I am glad to meet you 
+- C: MAIL FROM: 
+- S: 250 Ok 
+- C: RCPT TO: 
+- S: 250 Ok 
+- C: RCPT TO: 
+- S: 250 Ok 
+- C: DATA 
+- S: 354 End data with . 
+- C: From: "Bob Example" 
+- C: To: Alice Example 
+- C: Cc: theboss@example.com 
+- C: Date: Tue, 15 January 2008 16:02:43 -0500 
+- C: Subject: Test message 
+- C: 
+- C: Hello Alice. 
+- C: This is a test message with 5 header fields and 4 lines in the message body. 
+- C: Your friend, 
+- C: Bob 
+- C: . 
+- S: 250 Ok: queued as 12345 
+- C: QUIT 
+- S: 221 Bye 
+- {The server closes the connection}
+
+Email Spams (1) 
+- Also called junk emails 
+	- Anonymity: address and identity of the sender are concealed 
+	- Mass Mailing: sent to large groups of people 
+	- Unsolicited: not requested by the recipients 
+- Email spams grow steadily. 
+	- ~ 200 billion spam messages sent per day [2010] 
+	- > 97% of all emails sent over Internet are unwanted 
+- The negatives 
+	- Use up mailbox space 
+	- Click links in spam email may send users to phishing websites or sites that host malware. 
+	- May contain malware such as scripts or executable file attachments 
+	- Deception and fraud
+
+Email Spoofing/Phishing 
+- Spoofing is the creation of email messages with a forged sender address 
+	- Simple to do because the core protocols do no authentication 
+- Phishing is the attempt to acquire sensitive information such as usernames, passwords, and credit card details by masquerading as a trustworthy entity 
+	- Typically carried out by email spoofing 
+- Tips to identify spoofing and phishing email 
+	- Are the URLs legitimate? 
+	- Incorrect grammar/spelling 
+	- Suspicious attachments 
+	- Request for personal information 
+	- Urgent/Too good to be true 
+	- IP Reputation
+
+Anti-Spam Techniques (1) 
+- Detect spam email 
+	- Subject line: “I have money for you” 
+	- Attachments: .exe 
+	- Contents 
+	- DNSBLs: lists of domain names of known spammers 
+- End-user techniques 
+	- Report an unsolicited email: http://complaints.antispam.govt.nz 
+	- Do not expose your email address unless necessary 
+- Spammers can collect email addresses from websites, customer lists, newsgroups, and viruses which harvest users' address books. 
+	- Avoid responding to spams 
+	- Disposable email addresses
+
+Anti-Spam Techniques (2) 
+- Automated techniques 
+	- DNS-based blacklists 
+	- Pattern detection 
+	- Email filtering 
+		- Statistical content filtering 
+		- Checksum-based filtering 
+		- Rule-based filtering 
+		- Hybrid filtering 
+		- …
+
+Email Virus 
+- A virus (malware program) that comes within an attached file in an email message. 
+	- Trojan horse 
+	- macro virus 
+	- … 
+- Don’t trust attachments. Pay attention to the extensions of the attachments 
+	- Files with .EXE or .VBS extensions are always suspect 
+	- zip archives may contain executable codes 
+	- A full list of blocked extensions in Otago Email system http://www.otago.ac.nz/its/services/security/otago030398.html 
+- If uncertain, scan it using an anti-virus software
+
+
+Email Bomb 
+- A form of network abuse consisting of sending huge volumes of email to an address in attempt to overflow the mailbox or the server where the email address is hosted. 
+- Is a type of denial-of-service attack (DDoS) 
+- Methods of Email bombing 
+	- Mass mailing 
+		- Can be easily detected by spam filters 
+	- List linking 
+		- Mailing lists 
+	- Zip bombing 
+		- Zip files that take long time for the email server to unpack and check contents.
+
+Email Privacy 
+- PGP (Pretty Good Privacy) 
+	- Provides cryptographic privacy and authentication 
+	- Widely used to secure emails 
+	- Originally free, now also have commercial versions available 
+- S/MIME(Secure MIME): a standard for public key encryption and signing of MIME data 
+	- digital signing and message encryption using certificates 
+- STARTTLS: a TLS(SSL) layer on top of the SMTP connection that protects emails from being sniffed during transmission 
+	- encryption takes place between individual SMTP relays, not between the sender and the recipient.
+
+MTA Configuration (1) 
+- Auto-forwarding 
+	- Automatically forward emails to another mailbox 
+- Auto-reply 
+	- I am on vacation between ** and **
+
+MTA Configuration (2) 
+- Email fetching protocol 
+	- POP or IMAP? 
+- Mailing list 
+- Server security setting 
+- Digital signature and encryption
+

content/notes/cosc-301.md

@@ -43,5 +43,6 @@ https://www.cs.otago.ac.nz/cosc301/schedule.php
 - [ ] [[11-DNS]] need to read about security
 - [ ] [[12-DHCP]] need to study
 - [x] [[13-ssh]]
+- [ ] [[14-mail-servers]]
 
 # Info