Internet Receive Connector connections count must be set to default.
An XCCDF Rule
Description
<VulnDiscussion>Email 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 5000. If a limit is set too low, the connections pool may get filled. If attackers perceive the limit is too low, they could deny service to the Simple Mail Transfer Protocol (SMTP) server by using a connection count that exceeds the limit set. By setting the default configuration to 5000, attackers would need many more connections to cause denial of service.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>
- ID
- SV-43983r2_rule
- Severity
- Low
- Updated
Remediation - Manual Procedure
Noting the Internet-facing receive connector name, open the Exchange Management Shell and enter the following command:
Set-ReceiveConnector -Identity <'ReceiveConnector'> -MaxInboundConnection unlimited
If an alternate value is desired, obtain signoff with risk acceptance and document in the EDSP.