Attack surface reduction rules (Microsoft)

This article provides information about attack reduction rules:

• Supported operating system versions
• Supported configuration management systems
• Per-rule-descriptions
  • Rule descriptions
  • GUIDs
  • Configuration management system rule names

Public preview: Supported operating systems

The following table lists the supported operating systems for attack surface reduction rules that are currently prerelease product. The rules are listed alphabetical order.

(1) Refers to the modern, unified solution for Windows Server 2012 and 2016. For more information, see Onboard Windows Servers to the Defender for Endpoint service.

End Public Preview: Supported operating systems

Supported operating systems

The following table lists the supported operating systems for rules that are currently released to general availability. The rules are listed alphabetical order.

Supported configuration management systems

Links to information about configuration management system versions referenced in this table are listed below this table.

(1) You can configure attack surface reduction rules on a per-rule basis by using any rule’s GUID.

• Configuration Manager CB 1710
• Configuration Manager CB 1802
• Microsoft Endpoint Manager CB 1710
• System Center Configuration Manager (SCCM) CB 1710
  SCCM is now Microsoft Endpoint Configuration Manager.

Per rule descriptions

Block abuse of exploited vulnerable signed drivers

This rule prevents an application from writing a vulnerable signed driver to disk. In-the-wild, vulnerable signed drivers can be exploited by local applications – that have sufficient privileges – to gain access to the kernel. Vulnerable signed drivers enable attackers to disable or circumvent security solutions, eventually leading to system compromise.

The Block abuse of exploited vulnerable signed drivers rule does not block a driver already existing on the system from being loaded.

Intune Name: Block abuse of exploited vulnerable signed drivers (not yet available)

Configuration Manager name: Not yet available

GUID: 56a863a9-875e-4185-98a7-b882c64b5ce5

Block Adobe Reader from creating child processes

This rule prevents attacks by blocking Adobe Reader from creating processes.

Through social engineering or exploits, malware can download and launch payloads, and break out of Adobe Reader. By blocking child processes from being generated by Adobe Reader, malware attempting to use it as a vector are prevented from spreading.

Intune name: Process creation from Adobe Reader (beta)

Configuration Manager name: Not yet available

GUID: 7674ba52-37eb-4a4f-a9a1-f0f9a1619a2c

Advanced hunting action type:

• AsrAdobeReaderChildProcessAudited
• AsrAdobeReaderChildProcessBlocked

Dependencies: MDAV

Block all Office applications from creating child processes

This rule blocks Office apps from creating child processes. Office apps include Word, Excel, PowerPoint, OneNote, and Access.

Creating malicious child processes is a common malware strategy. Malware that abuse Office as a vector often run VBA macros and exploit code to download and attempt to run more payloads. However, some legitimate line-of-business applications might also generate child processes for benign purposes; such as spawning a command prompt or using PowerShell to configure registry settings.

Intune name: Office apps launching child processes

Configuration Manager name: Block Office application from creating child processes

GUID: d4f940ab-401b-4efc-aadc-ad5f3c50688a

Advanced hunting action type:

• AsrOfficeChildProcessAudited
• AsrOfficeChildProcessBlocked

Dependencies: MDAV

Block credential stealing from the Windows local security authority subsystem

This rule helps prevent credential stealing by locking down Local Security Authority Subsystem Service (LSASS).

LSASS authenticates users who sign in on a Windows computer. Microsoft Defender Credential Guard in Windows normally prevents attempts to extract credentials from LSASS. However, some organizations can’t enable Credential Guard on all of their computers because of compatibility issues with custom smartcard drivers or other programs that load into the Local Security Authority (LSA). In these cases, attackers can use hack tools like Mimikatz to scrape cleartext passwords and NTLM hashes from LSASS.

Intune name: Flag credential stealing from the Windows local security authority subsystem

Configuration Manager name: Block credential stealing from the Windows local security authority subsystem

GUID: 9e6c4e1f-7d60-472f-ba1a-a39ef669e4b2

Advanced hunting action type:

• AsrLsassCredentialTheftAudited
• AsrLsassCredentialTheftBlocked

Dependencies: MDAV

Block executable content from email client and webmail

This rule blocks the following file types from launching from email opened within the Microsoft Outlook application, or Outlook.com and other popular webmail providers:

• Executable files (such as .exe, .dll, or .scr)
• Script files (such as a PowerShell .ps, Visual Basic .vbs, or JavaScript .js file)

Intune name: Execution of executable content (exe, dll, ps, js, vbs, etc.) dropped from email (webmail/mail client) (no exceptions)

Microsoft Endpoint Manager name: Block executable content from email client and webmail

GUID: be9ba2d9-53ea-4cdc-84e5-9b1eeee46550

Advanced hunting action type:

• AsrExecutableEmailContentAudited
• AsrExecutableEmailContentBlocked

Dependencies: MDAV

Block executable files from running unless they meet a prevalence, age, or trusted list criterion

This rule blocks executable files, such as .exe, .dll, or .scr, from launching. Thus, launching untrusted or unknown executable files can be risky, as it might not be initially clear if the files are malicious.

Intune name: Executables that don't meet a prevalence, age, or trusted list criteria

Configuration Manager name: Block executable files from running unless they meet a prevalence, age, or trusted list criteria

GUID: 01443614-cd74-433a-b99e-2ecdc07bfc25

Advanced hunting action type:

• AsrUntrustedExecutableAudited
• AsrUntrustedExecutableBlocked

Dependencies: MDAV, Cloud Protection

Block execution of potentially obfuscated scripts

This rule detects suspicious properties within an obfuscated script.

Script obfuscation is a common technique that both malware authors and legitimate applications use to hide intellectual property or decrease script loading times. Malware authors also use obfuscation to make malicious code harder to read, which prevents close scrutiny by humans and security software.

Intune name: Obfuscated js/vbs/ps/macro code

Configuration Manager name: Block execution of potentially obfuscated scripts

GUID: 5beb7efe-fd9a-4556-801d-275e5ffc04cc

Advanced hunting action type:

• AsrObfuscatedScriptAudited
• AsrObfuscatedScriptBlocked

Dependencies: MDAV, AMSI

Block JavaScript or VBScript from launching downloaded executable content

This rule prevents scripts from launching potentially malicious downloaded content. Malware written in JavaScript or VBScript often acts as a downloader to fetch and launch other malware from the Internet.

Although not common, line-of-business applications sometimes use scripts to download and launch installers.

Intune name: js/vbs executing payload downloaded from Internet (no exceptions)

Configuration Manager name: Block JavaScript or VBScript from launching downloaded executable content

GUID: d3e037e1-3eb8-44c8-a917-57927947596d

Advanced hunting action type:

• AsrScriptExecutableDownloadAudited
• AsrScriptExecutableDownloadBlocked

Dependencies: MDAV, AMSI

Block Office applications from creating executable content

This rule prevents Office apps, including Word, Excel, and PowerPoint, from creating potentially malicious executable content, by blocking malicious code from being written to disk.

Malware that abuses Office as a vector might attempt to break out of Office and save malicious components to disk. These malicious components would survive a computer reboot and persist on the system. Therefore, this rule defends against a common persistence technique.

Intune name: Office apps/macros creating executable content

SCCM name: Block Office applications from creating executable content

GUID: 3b576869-a4ec-4529-8536-b80a7769e899

Advanced hunting action type:

• AsrExecutableOfficeContentAudited
• AsrExecutableOfficeContentBlocked

Dependencies: MDAV, RPC

Block Office applications from injecting code into other processes

This rule blocks code injection attempts from Office apps into other processes.

Attackers might attempt to use Office apps to migrate malicious code into other processes through code injection, so the code can masquerade as a clean process.

There are no known legitimate business purposes for using code injection.

This rule applies to Word, Excel, and PowerPoint.

Intune name: Office apps injecting code into other processes (no exceptions)

Configuration Manager name: Block Office applications from injecting code into other processes

GUID: 75668c1f-73b5-4cf0-bb93-3ecf5cb7cc84

Advanced hunting action type:

• AsrOfficeProcessInjectionAudited
• AsrOfficeProcessInjectionBlocked

Dependencies: MDAV

Block Office communication application from creating child processes

This rule prevents Outlook from creating child processes, while still allowing legitimate Outlook functions.

This rule protects against social engineering attacks and prevents exploiting code from abusing vulnerabilities in Outlook. It also protects against Outlook rules and forms exploits that attackers can use when a user’s credentials are compromised.

Intune name: Process creation from Office communication products (beta)

Configuration Manager name: Not available

GUID: 26190899-1602-49e8-8b27-eb1d0a1ce869

Advanced hunting action type:

• AsrOfficeCommAppChildProcessAudited
• AsrOfficeCommAppChildProcessBlocked

Dependencies: MDAV

Block persistence through WMI event subscription

This rule prevents malware from abusing WMI to attain persistence on a device.

Fileless threats employ various tactics to stay hidden, to avoid being seen in the file system, and to gain periodic execution control. Some threats can abuse the WMI repository and event model to stay hidden.

Intune name: Not available

Configuration Manager name: Not available

GUID: e6db77e5-3df2-4cf1-b95a-636979351e5b

Advanced hunting action type:

• AsrPersistenceThroughWmiAudited
• AsrPersistenceThroughWmiBlocked

Dependencies: MDAV, RPC

Block process creations originating from PSExec and WMI commands

This rule blocks processes created through PsExec and WMI from running. Both PsExec and WMI can remotely execute code, so there is a risk of malware abusing this functionality for command and control purposes, or to spread an infection throughout an organization’s network.

Intune name: Process creation from PSExec and WMI commands

Configuration Manager name: Not applicable

GUID: d1e49aac-8f56-4280-b9ba-993a6d77406c

Advanced hunting action type:

• AsrPsexecWmiChildProcessAudited
• AsrPsexecWmiChildProcessBlocked

Dependencies: MDAV

Block untrusted and unsigned processes that run from USB

With this rule, admins can prevent unsigned or untrusted executable files from running from USB removable drives, including SD cards. Blocked file types include executable files (such as .exe, .dll, or .scr)

Intune name: Untrusted and unsigned processes that run from USB

Configuration Manager name: Block untrusted and unsigned processes that run from USB

GUID: b2b3f03d-6a65-4f7b-a9c7-1c7ef74a9ba4

Advanced hunting action type:

• AsrUntrustedUsbProcessAudited
• AsrUntrustedUsbProcessBlocked

Dependencies: MDAV

Block Win32 API calls from Office macros

This rule prevents VBA macros from calling Win32 APIs.

Office VBA enables Win32 API calls. Malware can abuse this capability, such as calling Win32 APIs to launch malicious shellcode without writing anything directly to disk. Most organizations don’t rely on the ability to call Win32 APIs in their day-to-day functioning, even if they use macros in other ways.

Supported operating systems:

• Windows 10, version 1709
• Windows Server, version 1809
• Windows Server 2019
• Configuration Manager CB 1710

Intune name: Win32 imports from Office macro code

Configuration Manager name: Block Win32 API calls from Office macros

GUID: 92e97fa1-2edf-4476-bdd6-9dd0b4dddc7b

Advanced hunting action type:

• AsrOfficeMacroWin32ApiCallsAudited
• AsrOfficeMacroWin32ApiCallsBlocked

Dependencies: MDAV, AMSI

Use advanced protection against ransomware

This rule provides an extra layer of protection against ransomware. It uses both client and cloud heuristics to determine whether a file resembles ransomware. This rule does not block files that have one or more of the following characteristics:

• The file has already been found to be unharmful in the Microsoft cloud.
• The file is a valid signed file.
• The file is prevalent enough to not be considered as ransomware.

The rule tends to err on the side of caution to prevent ransomware.

Intune name: Advanced ransomware protection

Configuration Manager name: Use advanced protection against ransomware

GUID: c1db55ab-c21a-4637-bb3f-a12568109d35

Advanced hunting action type:

• AsrRansomwareAudited
• AsrRansomwareBlocked

Dependencies: MDAV, Cloud Protection

Source : Official Microsoft Brand
Editor by : BEST Antivirus KBS Team