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 main.cf 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.
- Postfix smtpd_banner option (Tips regarding configuring the smtpd_banner option)
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.
Lynis is a technical security audit tool for systems running Linux, UNIX, *BSD, and macOS. It is open source software and free to use. The project has an active community, and can also be found on GitHub.
Need more advanced features, like vulnerability scanning, or reporting installed software packages? Lynis Enterprise will collect more data and present it with an easy to use web interface.
Gain additional benefits: automating security audits, reporting, and the implementation of related security measures.
- Centralized management
- Prioritized plans
- Integration (API)
- Improvement snippets for tools like Ansible, Chef, Cfengine and Puppet