The SMTP service must not have the EXPN feature active.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-240446 | VRAU-SL-000625 | SV-240446r671079_rule | Medium |
| Description |
|---|
| 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. |
| STIG | Date |
|---|---|
| VMware vRealize Automation 7.x SLES Security Technical Implementation Guide | 2021-06-24 |
Details
| Check Text ( C-43679r671077_chk ) |
|---|
| 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. |
| Fix Text (F-43638r671078_fix) |
|---|
| Add "noexpn" to the "PrivacyOptions" flag in /etc/sendmail.cf |