The Exchange Sender Reputation filter must identify the spam block level.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-80557	EX16-ED-000390	SV-95267r1_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. Sender Reputation is antispam functionality that blocks messages according to many characteristics of the sender. Sender Reputation relies on persisted data about the sender to determine what action, if any, to take on an inbound message. This setting enables the threshold at which an email will be considered spam.

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. Sender Reputation is antispam functionality that blocks messages according to many characteristics of the sender. Sender Reputation relies on persisted data about the sender to determine what action, if any, to take on an inbound message. This setting enables the threshold at which an email will be considered spam.

STIG	Date
Microsoft Exchange 2016 Edge Transport Server Security Technical Implementation Guide	2019-03-12

Details

Check Text ( C-80289r1_chk )
Review the Email Domain Security Plan (EDSP). Determine the SrlBlockThreshold value. Open the Exchange Management Shell and enter the following command: Get-SenderReputationConfig \| Select Name, SrlBlockThreshold If the value of SrlBlockThreshold is not set to "6", this is a finding. or If the value of "SrlBlockThreshold" is set to a value other than "6" and has signoff and risk acceptance in the EDSP, this is not a finding.

Check Text ( C-80289r1_chk )

Review the Email Domain Security Plan (EDSP).

Determine the SrlBlockThreshold value.

Open the Exchange Management Shell and enter the following command:

Get-SenderReputationConfig | Select Name, SrlBlockThreshold

If the value of SrlBlockThreshold is not set to "6", this is a finding.

or

If the value of "SrlBlockThreshold" is set to a value other than "6" and has signoff and risk acceptance in the EDSP, this is not a finding.

Fix Text (F-87409r1_fix)
Update the EDSP to reflect the SrlBlockThreshold size. Open the Exchange Management Shell and enter the following command: Set-SenderReputationConfig -SrlBlockThreshold 6 or The value as identified by the EDSP that has obtained a signoff with risk acceptance.