The SMTP service HELP command must not be enabled.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-12006	GEN004540	SV-37504r4_rule		Medium

Description
The HELP command should be disabled to mask version information. The version of the SMTP service software could be used by attackers to target vulnerabilities present in specific software versions.

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

Details

Check Text ( C-36162r2_chk )
Check if Help is disabled. This rule is for "sendmail" only and not applicable to "Postfix". Procedure: # telnet localhost 25 > help If the help command returns any sendmail version information, this is a finding. If sendmail is not installed this check is not applicable.

Fix Text (F-31413r3_fix)
To disable the SMTP HELP command, clear the Sendmail help file. # echo -n > /etc/mail/helpfile