Illegal relay attacks refer to malicious activities that compromise the security of email servers. In these attacks, the perpetrator illegitimately uses a third-party email server to send bulk spam emails.
This technique is employed by spam senders to conceal their identity and avoid direct attribution when sending spam.
As a result, the email server ends up processing an abnormal amount of email traffic, which wastes server resources and degrades the performance of the email system.
Additionally, the unauthorized use of the email server’s IP address can lead to blacklisting issues, and the email server’s reputation may be tarnished.
Threat Pathways of Illegal Relay Attacks
Detection of Relay Servers
Attackers scan email servers to determine if the target email server allows relaying. A relay server refers to a server that permits email transmission from external sources.
Unauthorized Use of Relay Servers
After identifying relay servers, attackers determine the method to use these servers for sending spam emails. They do this by discovering unauthorized access methods for relay servers or exploiting vulnerabilities in legacy relay servers to use them without permission.
Sending Spam Emails
Attackers send a large volume of spam emails through the unauthorized relay server. They use relay servers to hide their actual IP address and to take advantage of the ability to send spam emails in bulk.
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Have you ever experienced your mail server being overwhelmed by a large volume of spam emails?