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V-4384

CAT III (Low)

The SMTP services SMTP greeting must not provide version information.

Rule ID

SV-46278r1_rule

STIG

SUSE Linux Enterprise Server v11 for System z Security Technical Implementation Guide

Version

V1R12

CCIs

CCI-000366

Discussion

The version of the SMTP service can be used by attackers to plan an attack based on vulnerabilities present in the specific version.

Check Content

To check for the version of either sendmail or Postfix being displayed in the greeting:

# telnet localhost 25

If a version number is displayed, this is a finding.

Fix Text

Ensure sendmail or Postfix has been configured to mask the version information.

Procedure
for sendmail:
Edit the /etc/mail/sendmail.mc file to mask the veresion number by editing the line with "dnl" as follows:
define(`confSMTP_LOGIN_MSG', ` Mail Server Ready ; $b')dnl
rebuild the sendmail.cf file.

for Postfix:
Examine the "smtpd_banner" line of /etc/postfix/main.conf and remove any "$mail_version" entry on it or comment the entire "smtpd_banner" line to use the default value which does not display the version information.