Allow Fallback to SSL 3.0 (Internet Explorer) must be disabled.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-250541	SRG-APP-000416	DTBI1100-IE11	SV-250541r942485_rule	2023-12-01	2

Description
This parameter ensures only DoD-approved ciphers and algorithms are enabled for use by the web browser by blocking an insecure fallback to SSL when TLS 1.0 or greater fails. Satisfies: SRG-APP-000514, SRG-APP-000555, SRG-APP-000625, SRG-APP-000630, SRG-APP-000635

ℹ️ Check
The policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Internet Explorer >> Security Features >> "Allow fallback to SSL 3.0 (Internet Explorer)" must be "Enabled", and "No Sites" selected from the drop-down box. If "Allow fallback to SSL 3.0 (Internet Explorer)" is not "Enabled" or any other drop-down option is selected, this is a finding. Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings. Criteria: If the value "EnableSSL3Fallback" is REG_DWORD=0, this is not a finding.

ℹ️ Check

The policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Internet Explorer >> Security Features >> "Allow fallback to SSL 3.0 (Internet Explorer)" must be "Enabled", and "No Sites" selected from the drop-down box. If "Allow fallback to SSL 3.0 (Internet Explorer)" is not "Enabled" or any other drop-down option is selected, this is a finding. Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings. Criteria: If the value "EnableSSL3Fallback" is REG_DWORD=0, this is not a finding.

✔️ Fix
Set the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Internet Explorer >> Security Features >> "Allow fallback to SSL 3.0 (Internet Explorer)" to "Enabled", and select "No Sites" from the drop-down box.