V-240446

Discussion

The SMTP EXPN function allows an attacker to determine if an account exists on a system, providing significant assistance to a brute force attack on user accounts. EXPN may also provide additional information concerning users on the system, such as the full names of account owners.

Check Content

Use the following command to check if EXPN is disabled:

# grep -v "^#" /etc/sendmail.cf |grep -i PrivacyOptions

If "noexpn" is not returned, this is a finding.