Why Email Server Security Matters

Nowadays, it is possible to quickly send an e-mail to a person or an institution on the other side of the world with a single click. Although it is thought that the developing technology will leave e-mail behind, e-mail is still among the most important communication tools today.

However, many people who use e-mail as a communication tool are not thoroughly familiar with e-mail technology because sending e-mail is a much more complex process. E-mail is sent via e-mail servers. On the way from sender to recipient, an e-mail passes through several e-mail servers.

See Also: Email Security Best Practices

In this case, as in all areas of the Internet, e-mail server security has a significant place. Before we come to e-mail server security, the part we need to talk about is e-mail servers. Email Server is a remote central server for email users that keeps all emails on a network.

We can compare the e-mail server to a post office. In the same way, people’s mail is stored in this virtual post office until it reaches its final destination. The e-mail server also communicates with the e-mail software users use, enabling them to access their mail through a database quickly.

See Also: PCI Compliance and Email Security

E-mail servers are examined under two different categories as sending servers and receiving servers. The most commonly known e-mail servers as shipping servers are SMTP (Simple Mail Transfer Protocol) servers.

POP3 (Post Office Protocol 3) or IMAP (Internet Message Access Protocol) servers are used as receiving servers. The IMAP or POP3 server protocols can always store a copy of the messages on the server.

In addition, all these processes, however long they may seem, take place in just seconds. Although e-mails go through such secure stages, one of the challenges of our age is insecure networks.

Of course, some malicious people use these insecure networks or rather create these networks. Therefore, we cannot say with certainty that all incoming e-mails are safe. It is necessary to give some information about these e-mails.

A virus is sent directly or embedded in it to many people via e-mail. Viruses sent via e-mail do not work now on the computer. The user clicks, ignoring the substance of the incoming email, and the computer is infected with the virus.

See Also: Public Key Cryptography and PGP Fundamentals

The attacker uses e-mail programs to run program codes such as HTML or JavaScript. Email content should not be opened without a virus scan to emails whose sender is unknown. Mails with viruses can generally be a screen saver, a game, a website extension, or any application with a .exe extension.

If such content is seen in an e-mail, it is necessary to scan them with virus programs on the computer. The biggest mistake is to open the mail content regardless of who the incoming mail comes from, and its content.

For starters, malicious people who wish to read e-mails between the sender and the receiver can stand between the sender and the receiver at any moment. He can edit, delete, or forward emails to a new destination in this method.

An example is the trojan virus. If a virus program is not used, the trojan placed on the computer can copy every e-mail you want to write, redirect it to a different location or even change its content. Trojan virus is a type of virus that uses the computer for its purposes. This virus is not a type of virus made to render the computer inoperable. There are simple and effective measures to be taken to protect against this virus.

The first of these is to use an advanced virus program. It is essential to keep virus programs up-to-date. When used in this way, the trojan virus becomes inhospitable on the computer.

In addition, malicious users can directly attack the other party to access e-mails directly. If successful, they will have the authority to do everything related to e-mail, as mentioned above.

See Also: What You Need to Know About Encrypted Communication

Sniffer; It is a technology that provides the task of monitoring and recording data traffic made in any known communication protocol on the Internet. Here, the malicious user can make this attack by listening to the network being used. Network listening and monitoring are generally called “sniffing.”

Using encryption and decryption software on the network is the most popular technique to eliminate this issue. However, in this way, one hundred percent security is not provided. However, there are several steps to be followed to minimize the damage.

What are the Email Security Protocols?

Email today is arguably the most critical application for personal and business communication over the Internet. With each new day, companies and individuals are increasingly revealing the sensitive information of recipients to the prevalence of malware, spam, phishing, and identity theft attacks. System verification records are added to make a communication tool like e-mail as secure as possible. SPF, DKIM, and DMARC are three alternative techniques of authenticating your email that all have the same goal of detecting bogus sender addresses in phishing or spam emails.

Sender Policy Framework (SPF)

When you send an email, it always includes hidden text that consists of the “return address” information for that email and information on the IP addresses and servers used to deliver the email.

A domain name system (DNS) record is what this is called. When spammers and Phishing emails “ ” an email address, they take a trusted address and place it in the “From” field of your incoming email, even if the email comes from a completely different source. This is to trick you into opening an email that you might have otherwise reasonably avoided.

By applying the Sender Policy Framework (SFP) validation protocol, you can detect and block email leakage by checking the IP address the email is requesting against the IP address listed in the SPF record. If all looks good, SPF authentication is confirmed, and the message is delivered.

Domain Keys Identified Mail (DKIM)

If you’re worried that information could be tampered with while your email is being transmitted, you can add a layer of security using DomainKeys Identified Mail (DKIM). This adds a domain identifier to the email that is unique and separate from any other identifiers.

This new information is kept secure by encrypting it with a public and private key. The public key is sent as part of the DNS record and is retained on the sender’s email server. The sender’s computer holds the private key.

The DKIM information in the public key is compared with the decrypted private key to identify if the email headers were altered during transmission or reception to promote trust between the send and receive servers.

Domain-based Message Authentication, Reporting & Conformance (DMARC)

Domain-based Message Authentication reporting and conformance (DMARC) is an additional layer of security authentication requiring SPF and DKIM to verify that an email is sent by the owner of the “friendly-from” domain that appears in the DNS report of the legitimate recipient. SPF and DKIM must be interlaced for this to happen, and at least one must be aligned.

If SPF and DKIM pass successfully, it confirms that the email came from an approved server, and the header information has not been changed. As for alignment, one of the two authentication protocols should show that the sender has “friendly” DNS space and has verified its correctness.

The “From” domain and the “return path” domain must match the SPF to align. If DMARC fails, the receiving computer can reject the email entirely or place the suspicious email somewhere other than the inbox, such as a spam folder.

How to Secure an Email Server?

1. Carefully configure mail relay options to avoid Open Relay

You must configure your mail relay parameter to be restrictive. You can define which domains or IP addresses your mail server forwards mail to for all mail servers.

This parameter, in other words, defines to whom your SMTP protocol should send mail. Misconfiguring this option can harm you because spammers can use your mail server (and network resources) as a gateway for spam, causing you to be blacklisted.

2. Control user access via SMTP authentication

By giving a username and password, SMTP Authentication is used to obtain permission to send mail from users using your server. This helps to prevent open relay and server misuse.

Only known accounts can send emails using your SMTP servers if they are configured correctly. When your mail server has a forwarded IP address, this setting is strongly recommended.

3. Set a connection limit to safeguard your server from denial-of-service attacks

You should limit the number of connections to your SMTP server. The main parameters used for the connection limit are the total number of connections, simultaneous connections, and maximum connection speed. The server hardware and daily load determine these parameters.

Updates may be required overtime to maintain optimal values ​​for these parameters. This can be very useful for reducing floods of spam and DoS attacks targeting your network infrastructure.

4. Enable reverse DNS to block fake senders

Before receiving a message, most messaging systems employ DNS lookups to verify the existence of the sender’s email domain. A reverse lookup could be used to detect fraudulent mailers.

When reverse DNS lookup is enabled, your SMTP verifies that the sending IP address matches both the host and domain names sent by the SMTP client in the EHLO / HELO command. This is invaluable for blocking messages that fail the address matching test.

5. Use DNSBL servers to combat incoming email abuse

One of the most basic configurations to protect your email server is to use DNS-based blacklists. Checking if the sending domain or IP is known to DNSBL servers worldwide can significantly reduce spam received.

Enabling this option and using the maximum number of DNSBL servers will significantly reduce the impact of spam. DNSBL servers list all known spammer’s IPs and domains for this purpose.

6. Enable SPF to prevent fraudulent sources

The Sender Policy Framework (SPF) is a method used to prevent fraudulent sender addresses. Today, nearly all malicious e-mail messages contain fake sender addresses.

The SPF control ensures that the sending MTA can send mail on behalf of the sender’s domain name. When SPF is enabled on your server, the sending server’s MX record (DNS Mail Exchange record) is validated before message transmission occurs.

7. Enable SURBL to verify message content

SURBL (Spam URI Real-time Block Lists) detects spam based on invalid or malicious links in a message. Having a SURBL filter helps protect users from malware and phishing attacks. Currently, not all mail servers support SURBL.

However, if your messaging server supports it, enabling it will increase the security of your server and the security of your entire network, as over 50% of Internet security threats come from email content.

8. Have local IP blacklists to block spammers

Having a local IP blocklist on your email server is crucial to countering specific spammers who only target you. Maintaining the list can take resources and time, but it provides absolute protection. The result is a fast and reliable way to prevent unwanted Internet connections from disturbing your messaging system.

9. For privacy reasons, encrypt POP3 and IMAP authentication.

POP3 and IMAP connections were not designed with security in mind from the start. As a result, they’re frequently employed in the absence of rigorous authentication. Because users transfer their credentials publicly over your mail server, hackers and malicious persons can readily obtain them, and this is a severe flaw.

SSL/TLS is the most well-known and straightforward method of implementing strong authentication; it is extensively used and regarded as reliable.

10. Make sure you have at least two MX records in case of a failover.

Usability necessitates the presence of a failover or failover arrangement. Setting up at least two MX records for each domain is highly advised, as one MX record is never enough to provide a consistent supply of mail to a given domain.

The first is set as primary, and the second is used as primary if it crashes for any reason. This configuration is done at the DNS Zone level.

How is Individual E-mail Security Provided?

While there is no way to guarantee that data is entirely secure, there are usually a few things that may be done to keep it safe. To briefly explain these under the headings Personal and Corporate Mail Security, below is a list of the best ways to protect email accounts.

1. Secure password usage: Many studies show how weak most passwords are. Therefore, a good password should be at least ten characters long, a combination of upper and lower case letters, and a unique character.

2. Beware of attachments: Especially in an e-mail sent by an unknown user, the e-mail should be scanned before opening the attachment. It’s worth noting that attachments infect PCs with 90% of viruses and malware.

3. Do not include sensitive information in email messages: Email is one of the primary sources of data leakage. If a person or organization needs to be given sensitive information, calling those people or organizations may be safer. If a sensitive document needs to be sent, different methods can be tried.

4. Not responding to spam or phishing emails: More than 3% of spam carries malware. Even though this appears to be a modest percentage, given the volume of spam emails sent every day, some of them may contain malware. So instead of replying to spam messages, they should be marked as spam immediately.

5. Beware of public Wi-Fi networks: Business people who check their email frequently take advantage of public Wi-Fi in many places while forgetting that public Wi-Fi is an excellent opportunity for hackers. If you still need to use such a Wi-Fi network, make sure you are connected to a legitimately free network regardless of the outcome.

How is Corporate E-mail Security Provided?

There are many ways to protect email accounts. Best practices for corporate email security include a two-pronged approach for businesses that cover employee training and comprehensive security protocols.

  • Provide ongoing security training to employees on email security risks and avoid exposure to email phishing attacks.
  • Employees should be required to use strong passwords and to update them regularly.
  • Email encryption should be used to protect both email content and attachments.
  • If the company allows its employees to access corporate email on personal devices, security best practices for BYOD should be implemented.
  • A data protection solution should be implemented to identify sensitive data and prevent it from being lost via e-mail.
  • Special tools should be used to scan messages and block emails containing malware or other malicious files before they reach end-users.

User Considerations for Email Security

E-mail is a technological system that carries out communication over electronic media. Quickly send pictures, music, videos, documents, etc., via email. Files can be sent.

This internet technology, which carries sensitive information, passes through many servers to reach its destination. E-mails carrying valuable data can become the target of attackers. In e-mail technology, which is the target or tool of attack in many ways; The sent e-mails can be stopped, changed, deleted, or forwarded to a different location at any time on the route between the sender and the other party.

You may be exposed to attacks by methods such as spam, phishing, baiting or phishing, or hoax. Also, many social media require email accounts, and all of these services provide a password reset feature via email.

To protect your emails from hackers, you can follow these suggestions:

  • Choose a strong password. The e-mail password must be changed periodically between 60-90 days. Must contain at least eight characters of upper and lower case letters, special characters, and numbers. Thus, it becomes robust against brute force attacks.
  • After choosing a strong password, use Two-factor authentication.
  • Select an e-mail service without password reset via e-mail.
  • Use different passwords for all your e-mail and social media accounts.
  • Do not use browsers’ password-saving features.
  • Check the e-mail address even if you receive an e-mail that you know and expect. Do not click on links in the e-mail unless necessary. Even if you need to open the link, it is best to copy the link address, paste it into the browser and open it.
  • Before opening invoices or statements that you have verified as being sent from the bank; Download them to your computer, scan them with your antivirus program.
  • Do not reply to e-mails from someone you do not expect or do not know.
  • Be sure to use security software with an E-mail content (spam) scanning feature and configure spam protection to scan incoming mails.

Tips for a Secure Email Sending

The sender’s personal information may include attachments and pictures, which he does not want to be shared with everyone. It may not be essential information, but this still does not mean that everyone should access it. Therefore, some security measures must be taken before sending an e-mail.

1-Think Before Posting

When sending an email, not everything needs to be encrypted. If you’re unsure whether or not it’s required to encrypt an email, consider the following questions:

  • Does the email contain anything of value (password, bank account, etc.)?
  • Is the message sensitive enough to include an expiration date?
  • Want to retrieve the e-mail?
  • Does the e-mail contain the private information of a person or an institution? If any of these questions is yes, it may be desirable to use an email encryption tool to protect the message.

2-Create a Safe Email Contacts List

A list of safe contacts is made. Friends, children, doctors, lawyers, or accountants should always receive encrypted, secure e-mail messages.

3-Use Two-Factor Authentication

It can be characterized as a two-factor security measure password and encryption that no one else has access to except the email owner. What needs to be done is usually to log into the account as usual. After this step, the user is asked for another password.

This password can be obtained in more than one way. Since those who want to enter the account need a second code besides the username and password, they cannot access the account owner’s account.

In summary, it is in the hands of individuals and institutions to ensure mail security. Considering the rules mentioned above, the damages that may occur can be partially avoided.

Surkay Baykarahttp://www.pcidssguide.com
A passionate Senior Information Security Consultant working at Biznet. Over the past 15+ years my professional career has included several positions beginning as a developer and IT administrator, working my way up to a senior Technical Performance Consultant before joining Biznet back in 2015. I had several different roles at Biznet, including Penetration Tester and PCI DSS QSA. In my job as a QSA, I found my passion and worked closely with the Audit and Compliance team. I've been working inside InfoSec for over 15 years, coming from a highly technical background. I have earned several certifications during my professional career including; CEH, CISA, CISSP, and PCI QSA.

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