The Many Ways Hackers Exploit Email Security Weaknesses

Email has been an essential communication channel for more than 50 years, and that’s not likely to change anytime soon. Despite the proliferation of alternative messaging platforms, global email volumes continue to rise each year. Nearly 350 billion emails are sent and received every day.

Hackers Exploit Email Phishing

The technology’s popularity also makes it a target, however.

It is the delivery vehicle for 91 percent of all cyberattacks, according to research from Deloitte. The volume of messages flowing in and out of organizations daily provides cover for malicious actors. Organizations are forced to evaluate an enormous amount of data to detect threats.

Additionally, most of email’s foundational protocols were developed decades ago and consequently lack modern security features. For example, the Simple Mail Transfer Protocol (SMTP) communication standard was developed in 1982 and lacks built-in authentication and encryption mechanisms.

Following are some of the common ways malicious actors exploit email’s inherent vulnerabilities:


Phishing attacks

  • This is the most common type of email exploit. Attackers use social engineering and technical manipulation, such as spoofing, to masquerade as legitimate users. Typically, they try to trick recipients into clicking on malicious links or providing sensitive information. This can lead to data breaches or unauthorized access to systems.

Email Spoofing

  • A lack of strong authentication makes it relatively easy for attackers to manipulate the “From” field in an email header and forge the sender’s email address. This allows them to send emails that appear to come from a legitimate source, which can be used for phishing or spreading malware.

Email is the delivery vehicle for 91 percent of all cyberattacks.

Man-in-the-middle Attacks

  • Attackers can intercept unencrypted communications between the sender and recipient, potentially modifying the email content or stealing sensitive information. Modification might involve inserting malicious links, changing details or adding malicious attachments designed to launch phishing, malware or ransomware attacks.


  • This is a version of a man-in-the-middle attack in which the attacker impersonates one or more parties in a conversation to send malicious instructions or requests that appear legitimate. In so-called “sock puppet” exploits, attackers use multiple fake accounts to make their targets believe they are engaged in an ongoing conversation with multiple colleagues. Typically, attackers will ultimately ask everyone in the thread to click on a link or download a document.

Directory Harvesting

  • In these attacks, cybercriminals attempt to gather valid email addresses from a target domain by systematically sending email queries to various username combinations. By analyzing the responses received — such as bounce-back messages indicating invalid addresses or successful deliveries — the attackers can deduce which email addresses are legitimate. This information can be used for subsequent targeted attacks.

Open Relay Abuse

  • Attackers can exploit misconfigured email servers to send mass quantities of spam, malware or phishing emails to a large number of recipients, often causing server overloads and email delivery delays. The attacker’s identity is effectively disguised because the server doesn’t properly validate the sender’s identity.


Harden Your Email Security Posture

Email is an indispensable business communication tool because it is fast, familiar and easy to use. However, all organizations must implement measures to ensure the security of their email systems and the sensitive data contained within them. Our Advanced Email Security Services harness an array of tools, services and expertise to help protect your email. Contact us to learn more.




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