Title

Inbound Connection Count Limit is not set to "Unlimited". (Cat III impact)

Discussion

E-Mail system availability depends in part on best practices strategies for setting tuning configurations. This configuration controls the maximum number of simultaneous inbound connections allowed to the SMTP server. By default, the number of simultaneous inbound connections is unlimited. If a limit is set and is too low, the connections pool may get filled. If attackers perceive there is a limit, they could deny service to the Simple Mail Transfer Protocol (SMTP) server using a limited connection count (set to unlimited), attackers would need many more connections to cause denial of service.

Check Content

Access the SMTP Inbound Connections configuration. Exchange System Manager >> administrative groups >> [administrative group] >> Servers >> [Server] >> Protocols >> SMTP >> [specific SMTP server] >> properties >> General tab The “Limit number of connections to” checkbox should be cleared. Criteria: If the "Limit Number of Connections to" is cleared, this is not a finding.

Fix Text

Set the Limit Inbound Connections limit. Procedure: Exchange System Manager >> administrative groups >> [administrative group] >> Servers >> [Server] >> Protocols >> SMTP >> [specific SMTP server] >> properties >> General tab Clear the “Limit number of connections to” checkbox.

Additional Identifiers

Rule ID: SV-20324r1_rule

Vulnerability ID: V-18692

Group Title:

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.