Detections
Analytics

AIX7-00-003117 - SMTP service must not have the EXPN or VRFY features active on AIX systems.

Information

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. 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.

Solution

Edit the "sendmail.cf" file and add or edit the following line:
O PrivacyOptions=goaway

Restart the "Sendmail" service:
# startsrc -s sendmail -a "-bd -q30m"

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_IBM_AIX_7-x_V3R3_STIG.zip

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6b., CAT|II, CCI|CCI-000366, Rule-ID|SV-215415r991589_rule, STIG-ID|AIX7-00-003117, STIG-Legacy|SV-101761, STIG-Legacy|V-91663, Vuln-ID|V-215415

Plugin: Unix

Control ID: 9de7a192458333aec71500af840daa952587b46f729d9a7396f1d813de39c216