The SMTP service's SMTP greeting must not provide version information.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-4384	GEN004560	SV-37505r2_rule		Low

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

STIG	Date
Red Hat Enterprise Linux 5 Security Technical Implementation Guide	2017-03-01

Details

Check Text ( C-36163r1_chk )
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 (F-31414r2_fix)
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.

Fix Text (F-31414r2_fix)

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.