Security Controls

MAIL-8818 - Postfix information leakage


To prevent announcing software or version to malicious people or scripts, it is advised to hide such information.



How to solve

It is common to see that software display their version number, name, or other details. While it may look innocent, it is a form of information leakage. It may provide attackers too much information during their reconnaissance phase, in which they try to determine what software is running. Especially when sharing software names together with the version, it becomes much easier to target that software.

For Postfix it is common to see it that it is running Postfix. Therefore change the "smtpd_banner" in and restart the daemon. The banner could be as simple as showing only "$myhostname ESMTP", to indicate this is a mail server, without revealing other details. The hostname is a required part of the standard, and easy to determine anyways.

Additional resources

Linux and Unix System Hardening

This information is provided as part of the Lynis community project. It is related to Lynis control MAIL-8818. All information should be considered as-is, without guarantees. Any advice or snippets should be tested before implementing in production environments.


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