Check: EX16-ED-000160
Microsoft Exchange 2016 Edge Transport Server STIG:
EX16-ED-000160
(in versions v2 r5 through v1 r1)
Title
Exchange Internet-facing Send connectors must specify a Smart Host. (Cat II impact)
Discussion
When identifying a "Smart Host" for the email environment, a logical Send connector is the preferred method. A Smart Host acts as an Internet-facing concentrator for other email servers. Appropriate hardening can be applied to the Smart Host, rather than at multiple locations throughout the enterprise. Failure to identify a Smart Host could default to each email server performing its own lookups (potentially through protective firewalls). Exchange servers should not be Internet facing and should therefore not perform any Smart Host functions. When the Exchange servers are Internet facing, they must be configured to identify the Internet-facing server that is performing the Smart Host function.
Check Content
Review the Email Domain Security Plan (EDSP). Determine the Internet-facing connectors. Open the Exchange Management Shell and enter the following command: Get-SendConnector | Select Name, Identity, SmartHosts, DNSRoutingEnabled For each send connector, if the value of "SmartHosts" does not return the Smart Host IP Address and the value for "DNSRoutingEnabled" is not set to "False", this is a finding.
Fix Text
Open the Exchange Management Shell and enter the following command: Set-SendConnector <'IdentityName'> -SmartHosts <'IP Address of Smart Host'> -DNSRoutingEnabled $false Note: The <IdentityName> value must be in single quotes. Repeat the procedures for each send connector.
Additional Identifiers
Rule ID: SV-221217r879633_rule
Vulnerability ID: V-221217
Group Title: SRG-APP-000213
Expert Comments
CCIs
Number | Definition |
---|---|
CCI-001178 |
The information system provides additional data origin authentication artifacts along with the authoritative name resolution data the system returns in response to external name/address resolution queries. |
Controls
Number | Title |
---|---|
SC-20 |
Secure Name / Address Resolution Service (Authoritative Source) |