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The SMTP service must not have the EXPN feature active.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
|---|---|---|---|---|
| V-89669 | VRAU-SL-000625 | SV-100319r1_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 | 2018-10-12 |
Details
| Check Text ( C-89361r1_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-96411r1_fix) |
|---|
| Add "noexpn" to the "PrivacyOptions" flag in /etc/sendmail.cf |