Which Attack Surface Reduction Rule Blocks Executables from %TEMP%?
A security administrator wants to block executable files from running from writable system directories such as %TEMP% and %APPDATA% on Windows devices. Which attack surface reduction (ASR) rule should be enabled?
⚠ Common exam trap
Watch out — candidates often confuse the 'Block executable files from running unless they meet a prevalence, age, or trusted list criterion' rule with the 'Block executable content from email client and webmail' rule, mistakenly thinking the latter covers all executable execution from writable directories when it only applies to email/webmail sources.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Block executable files from running unless they meet a prevalence, age, or trusted list criterion.
The ASR rule 'Block executable files from running unless they meet a prevalence, age, or trusted list criterion' (GUID: 01443614-cd74-433a-b99e-2ecdc07bfc25) is designed specifically to block executables (e.g., .exe, .dll, .scr) from running from writable locations like %TEMP% and %APPDATA% unless they have sufficient global prevalence, are older than a certain age, or are on a trusted list. This directly addresses the administrator's requirement to prevent untrusted executables from executing from these directories.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Block executable files from running unless they meet a prevalence, age, or trusted list criterion.
Why this is correct
This is the correct Attack Surface Reduction (ASR) rule, GUID 01443614-cd74-433a-b99e-2ecdc07bfc25, which blocks executables that lack sufficient prevalence, age, or a trusted-list entry. It leverages cloud-delivered reputation checks and admin-defined trusted files to stop unknown binaries that commonly execute from writable system directories such as %TEMP%, %APPDATA%, and C:\Users\Public, where persistence mechanisms are often planted. This directly enforces the requirement to block executable files from running from writable system locations while still allowing known legitimate software.
- ✗
Block Office communication application from creating child processes.
Why it's wrong here
This ASR rule prevents Office communication applications such as Outlook, Skype for Business, and Teams from spawning child processes like PowerShell or cmd.exe, which is a common post-exploitation technique for phishing payloads. However, it is scoped to process creation from Office communication software and does not evaluate the location or writability of the executable itself. It therefore fails to address the stem's requirement of blocking executable files from running from writable system directories, so it is not the correct rule.
- ✗
Block credential stealing from the Windows local security authority subsystem (lsass.exe).
Why it's wrong here
This ASR rule, also known as Block credential stealing from the Windows local security authority subsystem (lsass.exe), mitigates credential dumping by preventing suspicious processes from opening LSASS memory handles or accessing it in ways consistent with Mimikatz and other dumping tools. It targets Credential Guard and LSA protection bypass attempts, not the execution of arbitrary executables sourced from writable system paths. Since it does not restrict where binaries launch from, it cannot satisfy the given requirement.
- ✗
Block executable content from email client and webmail.
Why it's wrong here
This ASR rule blocks executable content such as .exe, .scr, .js, and .cmd files from being launched from email clients and webmail applications, primarily to stop malicious attachments that arrive via phishing emails. The rule is tied to the email client as the delivery vector, not to the file system location from which an executable runs. It does not provide any protection for writable system directories as a source of execution, making it an incorrect match for the stem.
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Related to this question
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Windows Autopilot Deployment
Key term
Attack surface reduction
Attack surface reduction is a set of security practices that minimizes the number of ways an attacker can access or exploit a system by removing unnecessary features, locking down configurations, and controlling software behavior.
Key term
Security
Security in IT is the practice of protecting systems, networks, and data from unauthorized access, damage, or theft.
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Same concept, more angles
2 more ways this is tested on MS-102
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A security administrator needs to block executable files (e.g., .exe, .ps1) from running from the %TEMP% folder on Windows devices to prevent common malware execution. Which attack surface reduction (ASR) rule should be enabled?
hard- ✓ A.Block executable files from running unless they meet a prevalence, age, or trusted list criterion
- B.Block executable content from email client and webmail
- C.Block Office applications from creating child processes
- D.Block credential stealing from the Windows local security authority subsystem (lsass.exe)
Why A: ASR rule 'Block executable files from running unless they meet a prevalence, age, or trusted list criterion' (GUID: 01443614-cd74-433a-b99e-2ecdc07bfc25) is designed specifically to block executables (including .exe, .ps1, .scr, .dll) from launching from locations like %TEMP%, %APPDATA%, and the Windows folder, which are common malware staging areas. This rule uses cloud-delivered reputation (prevalence and age) and a Microsoft-managed trusted list to allow legitimate files while blocking unknown or suspicious ones, directly addressing the requirement to prevent malware execution from %TEMP%.
Variation 2. A security administrator needs to block users from running portable executable files (e.g., .exe, .scr) that were downloaded from the internet on Windows devices. Which Attack Surface Reduction (ASR) rule should the administrator enable to meet this requirement?
hard- ✓ A.Block executable files from running unless they meet a prevalence, age, or trusted list criterion
- B.Block credential stealing from the Windows local security authority subsystem (lsass.exe)
- C.Block Adobe Reader from creating child processes
- D.Block persistence through WMI event subscription
Why A: The ASR rule 'Block executable files from running unless they meet a prevalence, age, or trusted list criterion' (GUID: 01443614-cd74-433a-b99e-2ecdc07bfc25) specifically targets executable files (e.g., .exe, .scr) that have been downloaded from the internet by checking their Mark-of-the-Web (MoTW) attribute. When enabled, this rule prevents execution of such files unless they meet criteria like high prevalence, sufficient age, or inclusion in a trusted list, directly addressing the requirement to block internet-downloaded portable executables.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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