The SMTP service must not have the VRFY feature active.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-4693	GEN004680	SV-4693r2_rule	ECSC-1	Low

Description
The VRFY (Verify) command allows an attacker to determine if an account exists on a system, providing significant assistance to a brute-force attack on user accounts. VRFY may provide additional information about users on the system, such as the full names of account owners.

STIG	Date
SOLARIS 10 SPARC SECURITY TECHNICAL IMPLEMENTATION GUIDE	2016-06-22

Details

Check Text ( C-705r2_chk )
Determine if VRFY is disabled. Procedure: # telnet localhost 25 vrfy root If the command does not return a 500 error code of command unrecognized, this is a finding. OR Locate the sendmail.cf configuration file. Procedure: # find / -name sendmail.cf -print # grep -v "^#" \|grep -i "(goaway\|vrfy)" Verify the VRFY command is disabled with an entry in the sendmail.cf file that reads as one of the following: Opnovrfy O PrivacyOptions=novrfy Opgoaway O PrivacyOptions=goaway (Other privacy options, such as noexpn or noetrn, may be included in the same line, separated by commas. The goaway option encompasses a number of privacy options, including novrfy.) If the VRFY command is not disabled, this is a finding.

Check Text ( C-705r2_chk )

Determine if VRFY is disabled.

Procedure:
# telnet localhost 25
vrfy root

If the command does not return a 500 error code of command unrecognized, this is a finding.

OR

Locate the sendmail.cf configuration file.

Procedure:
# find / -name sendmail.cf -print
# grep -v "^#" |grep -i "(goaway|vrfy)"

Verify the VRFY command is disabled with an entry in the sendmail.cf file that reads as one of the following:

Opnovrfy
O PrivacyOptions=novrfy
Opgoaway
O PrivacyOptions=goaway

(Other privacy options, such as noexpn or noetrn, may be included in the same line, separated by commas. The goaway option encompasses a number of privacy options, including novrfy.) If the VRFY command is not disabled, this is a finding.

Fix Text (F-4621r2_fix)
If Sendmail is running, add the line Opnovrfy to the Sendmail configuration file, usually located in /etc/sendmail.cf. For other mail servers, contact the vendor for information on how to disable the verify command. Newer versions of Sendmail are available at http://www.sendmail.org or from ftp://ftp.cs.berkeley.edu/ucb/sendmail.