Windows Update must not obtain updates from other PCs on the Internet.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-220835	WN10-CC-000206	SV-220835r569187_rule		Low

Description
Windows 10 allows Windows Update to obtain updates from additional sources instead of Microsoft. In addition to Microsoft, updates can be obtained from and sent to PCs on the local network as well as on the Internet. This is part of the Windows Update trusted process, however to minimize outside exposure, obtaining updates from or sending to systems on the Internet must be prevented.

STIG	Date
Windows 10 Security Technical Implementation Guide	2021-08-18

Details

Check Text ( C-22550r554990_chk )
If the following registry value does not exist or is not configured as specified, this is a finding: Registry Hive: HKEY_LOCAL_MACHINE Registry Path: \SOFTWARE\Policies\Microsoft\Windows\DeliveryOptimization\ Value Name: DODownloadMode Value Type: REG_DWORD Value: 0x00000000 (0) - No peering (HTTP Only) 0x00000001 (1) - Peers on same NAT only (LAN) 0x00000002 (2) - Local Network / Private group peering (Group) 0x00000063 (99) - Simple download mode, no peering (Simple) 0x00000064 (100) - Bypass mode, Delivery Optimization not used (Bypass) A value of 0x00000003 (3), Internet, is a finding. v1507 LTSB: Domain joined systems: Verify the registry value above. If the value is not 0x00000000 (0) or 0x00000001 (1), this is a finding. Standalone systems (configured in Settings): If the following registry value does not exist or is not configured as specified, this is a finding: Registry Hive: HKEY_LOCAL_MACHINE Registry Path: \SOFTWARE\Microsoft\Windows\CurrentVersion\DeliveryOptimization\Config\ Value Name: DODownloadMode Value Type: REG_DWORD Value: 0x00000000 (0) - Off 0x00000001 (1) - LAN

Check Text ( C-22550r554990_chk )

If the following registry value does not exist or is not configured as specified, this is a finding:

Registry Hive: HKEY_LOCAL_MACHINE
Registry Path: \SOFTWARE\Policies\Microsoft\Windows\DeliveryOptimization\

Value Name: DODownloadMode

Value Type: REG_DWORD
Value: 0x00000000 (0) - No peering (HTTP Only)
0x00000001 (1) - Peers on same NAT only (LAN)
0x00000002 (2) - Local Network / Private group peering (Group)
0x00000063 (99) - Simple download mode, no peering (Simple)
0x00000064 (100) - Bypass mode, Delivery Optimization not used (Bypass)

A value of 0x00000003 (3), Internet, is a finding.

v1507 LTSB:
Domain joined systems:
Verify the registry value above.
If the value is not 0x00000000 (0) or 0x00000001 (1), this is a finding.

Standalone systems (configured in Settings):
If the following registry value does not exist or is not configured as specified, this is a finding:

Registry Hive: HKEY_LOCAL_MACHINE
Registry Path: \SOFTWARE\Microsoft\Windows\CurrentVersion\DeliveryOptimization\Config\

Value Name: DODownloadMode

Value Type: REG_DWORD
Value: 0x00000000 (0) - Off
0x00000001 (1) - LAN

Fix Text (F-22539r554991_fix)
Configure the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Delivery Optimization >> "Download Mode" to "Enabled" with any option except "Internet" selected. Acceptable selections include: Bypass (100) Group (2) HTTP only (0) LAN (1) Simple (99) v1507 (LTSB) does not include this group policy setting locally. For domain joined systems, configure through domain group policy as "HTTP only (0)" or "Lan (1)". Standalone systems configure using Settings >> Update & Security >> Windows Update >> Advanced Options >> "Choose how updates are delivered" with either "Off" or "PCs on my local network" selected.

Fix Text (F-22539r554991_fix)

Configure the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Delivery Optimization >> "Download Mode" to "Enabled" with any option except "Internet" selected.

Acceptable selections include:
Bypass (100)
Group (2)
HTTP only (0)
LAN (1)
Simple (99)

v1507 (LTSB) does not include this group policy setting locally. For domain joined systems, configure through domain group policy as "HTTP only (0)" or "Lan (1)". Standalone systems configure using Settings >> Update & Security >> Windows Update >> Advanced Options >> "Choose how updates are delivered" with either "Off" or "PCs on my local network" selected.