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The Exchange SMTP automated banner response must not reveal server details.


Finding ID Version Rule ID IA Controls Severity
V-259707 EX19-MB-000232 SV-259707r942435_rule Medium
Automated connection responses occur as a result of FTP or Telnet connections when connecting to those services. They report a successful connection by greeting the connecting client and stating the name, release level, and (often) additional information regarding the responding product. While useful to the connecting client, connection responses can also be used by a third party to determine operating system or product release levels on the target server. The result can include disclosure of configuration information to third parties, paving the way for possible future attacks. For example, when querying the SMTP service on port 25, the default response looks similar to this one: 220 exchange.mydomain.org Microsoft ESMTP MAIL Service ready at Tuesday, 23 Nov 2021 13:43:00 -0500 Changing the response to hide local configuration details reduces the attack profile of the target.
Microsoft Exchange 2019 Mailbox Server Security Technical Implementation Guide 2024-01-10


Check Text ( C-63446r942433_chk )
Open the Exchange Management Shell and enter the following command:

Get-ReceiveConnector | Select-Object -Property Name, Identity, Banner

For each Receive connector, if the value of "Banner" is not set to "220 SMTP Server Ready", this is a finding.
Fix Text (F-63354r942434_fix)
Open the Exchange Management Shell and enter the following command:

Set-ReceiveConnector -Identity <'IdentityName'> -Banner '220 SMTP Server Ready'

Note: The and 220 SMTP Server Ready values must be in quotes.

Repeat the procedures for each Receive connector.