As a universally implemented protocol, email should be a target
for attacks and risk ; due to the very sensitive nature of the data or information that is transmitted.
E-mail at its core is safe because it does not transmit directly executable(binary) code.
But an e-mail client starts adding features to be more of a collaboration tool, such as Outlook which embed malcode that has chances of being decoded and launched.
An e-mail protocol like Post Office Protocol (POP), was used in the clear,
which means when a mail was received, it was transmitted with the POP3 protocol.
In such case, the entire e-mail fit into one packet and opportunity to capture packets and read e-mail content isn't off-topic.
Capturing and modifying of e-mail can be done either as a man-in-the-middle attack (using ARP spoofing tool, such as ettercap) or as a replay attack.
Man-in-the-middle attacks are best avoided by using encryption and digital signing of messages.
On the other hand, Spam DoS attacks are a result of spammers using false domains in the e-mails they send.
The most danger type of these attacks is when a spammer forges an address.
Spam attacks avoided by referencing a blacklist which is a database of known internet addresses (by domain names or IP addresses) used by spammers.
Blacklisted addresses return invalid responses so the server rejects the e-mail.
Proper e-mail authentication is also a security concern.
-Login authentication : user name and password passed separately encoded with base64.
The user name and password are then used to authenticate to the mail server.
- onPOP before SMTP : preventing spammers from using a mail server relay.
SMTP relaying is permitted by an IP address if that IP address has participated in a valid POP session in the prior X minutes.
The POP protocol requires a valid password so spammers will not be able to use POP prior to using the mail server for relaying.
A mail relay sits in the DMZ outside the perimeter firewall with a benefit having all mail received first by this mail relay which can check for unwanted scripts, viruses, and questionable attachments and also a good place to put spam protection, such as blacklist monitoring and spam filtering.
Securing e-mail traffic: discussed previouslyCreating a secure tunnel for using less secure e-mail protocols can be a strong method of protecting the privacy and integrity of the e-mail.
With an SSH tunnel, we can still have the protection of the SSH encryption, in SMTP/POPing.
Later talking about SPF, DomainKeys ...etc
