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Exchange messages with a blank sender field must be filtered.


Overview

Finding ID Version Rule ID IA Controls Severity
V-221233 EX16-ED-000340 SV-221233r612603_rule Medium
Description
By performing filtering at the perimeter, up to 90 percent of spam, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the mail server environment. Anonymous email (messages with blank sender fields) cannot be replied to. Messages formatted in this way may be attempting to hide their true origin to avoid responses or to spam any receiver with impunity while hiding their source of origination. Rather than spend resources and risk infection while evaluating them, it is recommended that these messages be filtered immediately upon receipt and not forwarded to end users.
STIG Date
Microsoft Exchange 2016 Edge Transport Server Security Technical Implementation Guide 2022-06-09

Details

Check Text ( C-22948r411825_chk )
This requirement is N/A for SIPR enclaves.

This requirement is N/A if the organization subscribes to EEMSG or other similar DoD enterprise protections for email services.

Open the Exchange Management Shell and enter the following command:

Get-SenderFilterConfig | Select Name, BlankSenderBlockingEnabled

If the value of "BlankSenderBlockingEnabled" is not set to "True", this is a finding.
Fix Text (F-22937r411826_fix)
Open the Exchange Management Shell and enter the following command:

Set-SenderFilterConfig -BlankSenderBlockingEnabled $true