Information
This rule prevents the execution of certain commands to restart the system in Safe Mode.
Rule ID and name:
- 33ddedf1-c6e0-47cb-833e-de6133960387 (Block rebooting machine in Safe Mode)
The recommended state for this setting is: 33ddedf1-c6e0-47cb-833e-de6133960387:1 (Block).
Note: More information on ASR rules can be found at the following link: Use Attack surface reduction rules to prevent malware infection | Microsoft Docs https://docs.microsoft.com/en-us/windows/security/threat-protection/windows-defender-exploit-guard/attack-surface-reduction-exploit-guard
Note #2: Safe Mode is still accessible manually from the Windows Recovery Environment.
Attack surface reduction helps prevent actions and apps that are typically used by exploit-seeking malware to infect machines.
When a system is in Safe Mode, many security controls are disabled or operate with reduced functionality, which can allow attackers to execute tampering commands or encrypt files. This rule mitigates that risk by blocking commonly abused commands, such as 'bcdedit' and 'bootcfg', that are used to restart systems into Safe Mode.
Solution
To establish the recommended configuration via GP, set the following UI path to 33ddedf1-c6e0-47cb-833e-de6133960387 with a value of 1 :
Computer Configuration\Policies\Administrative Templates\Windows Components\Microsoft Defender Antivirus\Microsoft Defender Exploit Guard\Attack Surface Reduction\Configure Attack Surface Reduction rules: Set the state for each ASR rule
Note: This Group Policy path is provided by the Group Policy template WindowsDefender.admx/adml that is included with the Microsoft Windows 10 Release 1709 Administrative Templates (or newer).
Impact:
The system will not start in Safe Mode when using commands such as 'bcdedit' and 'bootcfg'.