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Disable Defender Antivirus "Block at First Sight" feature

Overview​

About this script

This script improves your privacy on Windows.

These changes use Windows system commands to update your settings.

This script disables the "Block at first sight".

Block at first sight is Defender Antivirus feature 1 2 3 4. It protects against threats by quickly detecting and blocking new malware 1. When Defender Antivirus encounters a suspicious file it can't identify, it consults its cloud protection backend 1. The cloud backend uses heuristics, machine learning, and automated analysis to identify malicious files 1. This back-end is part of Cloud Protection 1. It is also known as Microsoft Active Protection Service (MAPS) 1 2 3 or SpyNet 2.

This feature is enabled by default 4, depending on other configurations 1 2. The feature is included in Defender for Endpoint suite 1.

Automatically sending files to Microsoft's cloud 1 3 raises significant privacy concerns. This script improves your privacy by preventing automatic file uploads to Microsoft. It may also improve system performance by reducing background network activity.

However, disabling this feature may reduce your device and network protection levels 1 3. The Defense Information Systems Agency (DISA) recommends keeping this feature enabled for additional security 3.

Caution

This change enhances privacy but may reduce overall system security.

Technical Details​

This script configures the option by:

  • Using the Defender CLI to set the DisableBlockAtFirstSeen preference 4.
  • Configuring HKLM\Software\Microsoft\Windows Defender\SpyNet!DisableBlockAtFirstSeen to mimic the CLI. Tests indicate that the CLI sets this registry key.
  • Setting the registry key HKLM\Software\Policies\Microsoft\Windows Defender\SpyNet!DisableBlockAtFirstSeen to configure the group policy 2 3.

This script uses Batch (batchfile) scripting language.

Use with Caution

This script is only recommended if you understand its implications. Some non-critical or features may no longer function correctly after running this script.

Implementation Details

  • Language: batch

  • Required Privileges: Administrator rights

  • Compatibility: Windows only

  • Reversibility: Can be undone using provided revert script

Explore Categories​

This action belongs to Disable Defender Antivirus cloud protection category. This category contains scripts that disable or limit Microsoft Defender's cloud-based protection features. Microsoft Defender's cloud protection is also known as Microsoft MAPS (Microsoft Active Protection Service) or Microsoft SpyNet. It is an online community that helps detect and prevent the... Read more on category page ▶

Apply now​

Choose one of three ways to apply:

  1. Automatically via privacy.sexy: The easiest and safest option.
  2. Manually by downloading: Requires downloading a file.
  3. Manually by copying: Advanced flexibility.

Alternative 1. Apply with Privacy.sexy​

privacy.sexy is free and open-source application that lets securely apply this action easily.

Open privacy.sexy

You can fully restore this action (revert back to the original behavior) using the application.

privacy.sexy instructions
  1. Open or download the desktop application
  2. Search for the script name: Disable Defender Antivirus "Block at First Sight" feature.
  3. Check the script by clicking on the checkbox.
  4. Click on Run button at the bottom of the page.

Alternative 2. Download​

Irreversible Changes

This script is irreversible, meaning there is no straightforward method to restore changes once applied. Exercise caution before running, restoring it may not be possible.

  1. Download the script file by clicking on the button below:

    Download script

  2. Run the script file by clicking on it.

Download revert script​

This file restores your system to its original state, before this script is applied.

Download restore script

Alternative 3. Copy​

This is for advanced users. Consider automatically applying or downloading the script for simpler way.

  1. Open Command Prompt as administrator.
HELP: Step-by-step guide

  1. Click on Start menu

  2. Type cmd

  3. Right click on Command Prompt select Run as administrator

  4. Click on Yes to run Command Prompt

Animation showing how to open terminal as administrator on Windows 11

  1. Copy the following code:
Code to apply changes
PowerShell -ExecutionPolicy Unrestricted -Command "$propertyName = 'DisableBlockAtFirstSeen'; $value = $True; if((Get-MpPreference -ErrorAction Ignore).$propertyName -eq $value) { Write-Host "^""Skipping. `"^""$propertyName`"^"" is already `"^""$value`"^"" as desired."^""; exit 0; }; $command = Get-Command 'Set-MpPreference' -ErrorAction Ignore; if (!$command) { Write-Warning 'Skipping. Command not found: "^""Set-MpPreference"^"".'; exit 0; }; if(!$command.Parameters.Keys.Contains($propertyName)) { Write-Host "^""Skipping. `"^""$propertyName`"^"" is not supported for `"^""$($command.Name)`"^""."^""; exit 0; }; try { Invoke-Expression "^""$($command.Name) -Force -$propertyName `$value -ErrorAction Stop"^""; Set-MpPreference -Force -DisableBlockAtFirstSeen $value -ErrorAction Stop; Write-Host "^""Successfully set `"^""$propertyName`"^"" to `"^""$value`"^""."^""; exit 0; } catch { if ( $_.FullyQualifiedErrorId -like '*0x800106ba*') { Write-Warning "^""Cannot $($command.Name): Defender service (WinDefend) is not running. Try to enable it (revert) and re-run this?"^""; exit 0; } elseif (($_ | Out-String) -like '*Cannot convert*') { Write-Host "^""Skipping. Argument `"^""$value`"^"" for property `"^""$propertyName`"^"" is not supported for `"^""$($command.Name)`"^""."^""; exit 0; } else { Write-Error "^""Failed to set using $($command.Name): $_"^""; exit 1; }; }"
:: Set the registry value: "HKLM\Software\Policies\Microsoft\Windows Defender\SpyNet!DisableBlockAtFirstSeen"
PowerShell -ExecutionPolicy Unrestricted -Command "$registryPath = 'HKLM\Software\Policies\Microsoft\Windows Defender\SpyNet'; $data = '1'; reg add 'HKLM\Software\Policies\Microsoft\Windows Defender\SpyNet' /v 'DisableBlockAtFirstSeen' /t 'REG_DWORD' /d "^""$data"^"" /f"
:: Set the registry value: "HKLM\Software\Microsoft\Windows Defender\SpyNet!DisableBlockAtFirstSeen"
PowerShell -ExecutionPolicy Unrestricted -Command "function Invoke-AsTrustedInstaller($Script) { $principalSid = [System.Security.Principal.SecurityIdentifier]::new('S-1-5-80-956008885-3418522649-1831038044-1853292631-2271478464'); $principalName = $principalSid.Translate([System.Security.Principal.NTAccount]); $streamFile = New-TemporaryFile; $scriptFile = New-TemporaryFile; try { $scriptFile = Rename-Item -LiteralPath $scriptFile -NewName ($scriptFile.BaseName + '.ps1') -Force -PassThru; $Script | Out-File $scriptFile -Encoding UTF8; $taskName = "^""privacy$([char]0x002E)sexy invoke"^""; schtasks.exe /delete /tn $taskName /f 2>&1 | Out-Null; $executionCommand = "^""powershell.exe -ExecutionPolicy Bypass -File '$scriptFile' *>&1 | Out-File -FilePath '$streamFile' -Encoding UTF8"^""; $action = New-ScheduledTaskAction -Execute 'powershell.exe' -Argument "^""-ExecutionPolicy Bypass -Command `"^""$executionCommand`"^"""^""; $settings = New-ScheduledTaskSettingsSet -AllowStartIfOnBatteries -DontStopIfGoingOnBatteries; Register-ScheduledTask -TaskName $taskName -Action $action -Settings $settings -Force -ErrorAction Stop | Out-Null; try { ($scheduleService = New-Object -ComObject Schedule.Service).Connect(); $scheduleService.GetFolder('\').GetTask($taskName).RunEx($null, 0, 0, $principalName) | Out-Null; $timeout = (Get-Date).AddMinutes(5); Write-Host "^""Running as $principalName"^""; while ((Get-ScheduledTaskInfo $taskName).LastTaskResult -eq 267009) { Start-Sleep -Milliseconds 200; if ((Get-Date) -gt $timeout) { Write-Warning 'Skipping: Timeout'; break; }; }; if (($result = (Get-ScheduledTaskInfo $taskName).LastTaskResult) -ne 0) { Write-Error "^""Failed, due to exit code: $result."^""; } } finally { schtasks.exe /delete /tn $taskName /f | Out-Null; }; Get-Content $streamFile } finally { Remove-Item $streamFile, $scriptFile; }; }; $cmd = '$registryPath = ''HKLM\Software\Microsoft\Windows Defender\SpyNet'''+"^""`r`n"^""+'$data = ''1'''+"^""`r`n"^""+''+"^""`r`n"^""+'reg add ''HKLM\Software\Microsoft\Windows Defender\SpyNet'' `'+"^""`r`n"^""+'    /v ''DisableBlockAtFirstSeen'' `'+"^""`r`n"^""+'    /t ''REG_DWORD'' `'+"^""`r`n"^""+'    /d "^""$data"^"" `'+"^""`r`n"^""+'    /f'; Invoke-AsTrustedInstaller $cmd"
  1. Right click on command prompt to paste it.
  2. Press Enter to apply remaining code.

Copy restore code​

Copy and run the following code to restore changes:

Revert code
PowerShell -ExecutionPolicy Unrestricted -Command "$propertyName = 'DisableBlockAtFirstSeen'; $defaultValue = $False; $setDefaultOnWindows10 = $true <# $false #>; $setDefaultOnWindows11 =  $false; $osVersion = [System.Environment]::OSVersion.Version; function Test-IsWindows10 { ($osVersion.Major -eq 10) -and ($osVersion.Build -lt 22000) }; function Test-IsWindows11 { ($osVersion.Major -gt 10) -or (($osVersion.Major -eq 10) -and ($osVersion.Build -ge 22000)) }; <# ------ Set-MpPreference ------ #>; if(($setDefaultOnWindows10 -and (Test-IsWindows10)) -or ($setDefaultOnWindows11 -and (Test-IsWindows11))) { if((Get-MpPreference -ErrorAction Ignore).$propertyName -eq $defaultValue) { Write-Host "^""Skipping. `"^""$propertyName`"^"" is already configured as desired `"^""$defaultValue`"^""."^""; exit 0; }; $command = Get-Command 'Set-MpPreference' -ErrorAction Ignore; if (!$command) { Write-Warning 'Skipping. Command not found: "^""Set-MpPreference"^"".'; exit 1; }; if(!$command.Parameters.Keys.Contains($propertyName)) { Write-Host "^""Skipping. `"^""$propertyName`"^"" is not supported for `"^""$($command.Name)`"^""."^""; exit 0; }; try { Invoke-Expression "^""$($command.Name) -Force -$propertyName `$defaultValue -ErrorAction Stop"^""; Write-Host "^""Successfully restored `"^""$propertyName`"^"" to its default `"^""$defaultValue`"^""."^""; exit 0; } catch { if ($_.FullyQualifiedErrorId -like '*0x800106ba*') { Write-Warning "^""Cannot $($command.Name): Defender service (WinDefend) is not running. Try to enable it (revert) and re-run this?"^""; } else { Write-Error "^""Failed to set using $($command.Name): $_"^""; }; exit 1; }; }; <# ------ Remove-MpPreference ------ #>; $command = Get-Command 'Remove-MpPreference' -ErrorAction Ignore; if (!$command) { Write-Warning 'Skipping. Command not found: "^""Remove-MpPreference"^"".'; exit 1; }; if(!$command.Parameters.Keys.Contains($propertyName)) { Write-Host "^""Skipping. `"^""$propertyName`"^"" is not supported for `"^""$($command.Name)`"^""."^""; exit 0; }; try { Invoke-Expression "^""$($command.Name) -Force -$propertyName -ErrorAction Stop"^""; Write-Host "^""Successfully restored `"^""$propertyName`"^"" to its default."^""; exit 0; } catch { if ($_.FullyQualifiedErrorId -like '*0x800106ba*') { Write-Warning "^""Cannot $($command.Name): Defender service (WinDefend) is not running. Try to enable it (revert) and re-run this?"^""; } else { Write-Error "^""Failed to set using $($command.Name): $_"^""; }; exit 1; }"
:: Delete the registry value "HKLM\Software\Policies\Microsoft\Windows Defender\SpyNet!DisableBlockAtFirstSeen"
PowerShell -ExecutionPolicy Unrestricted -Command "reg delete 'HKLM\Software\Policies\Microsoft\Windows Defender\SpyNet' /v 'DisableBlockAtFirstSeen' /f 2>$null"
:: Delete the registry value "HKLM\Software\Microsoft\Windows Defender\SpyNet!DisableBlockAtFirstSeen"
PowerShell -ExecutionPolicy Unrestricted -Command "function Invoke-AsTrustedInstaller($Script) { $principalSid = [System.Security.Principal.SecurityIdentifier]::new('S-1-5-80-956008885-3418522649-1831038044-1853292631-2271478464'); $principalName = $principalSid.Translate([System.Security.Principal.NTAccount]); $streamFile = New-TemporaryFile; $scriptFile = New-TemporaryFile; try { $scriptFile = Rename-Item -LiteralPath $scriptFile -NewName ($scriptFile.BaseName + '.ps1') -Force -PassThru; $Script | Out-File $scriptFile -Encoding UTF8; $taskName = "^""privacy$([char]0x002E)sexy invoke"^""; schtasks.exe /delete /tn $taskName /f 2>&1 | Out-Null; $executionCommand = "^""powershell.exe -ExecutionPolicy Bypass -File '$scriptFile' *>&1 | Out-File -FilePath '$streamFile' -Encoding UTF8"^""; $action = New-ScheduledTaskAction -Execute 'powershell.exe' -Argument "^""-ExecutionPolicy Bypass -Command `"^""$executionCommand`"^"""^""; $settings = New-ScheduledTaskSettingsSet -AllowStartIfOnBatteries -DontStopIfGoingOnBatteries; Register-ScheduledTask -TaskName $taskName -Action $action -Settings $settings -Force -ErrorAction Stop | Out-Null; try { ($scheduleService = New-Object -ComObject Schedule.Service).Connect(); $scheduleService.GetFolder('\').GetTask($taskName).RunEx($null, 0, 0, $principalName) | Out-Null; $timeout = (Get-Date).AddMinutes(5); Write-Host "^""Running as $principalName"^""; while ((Get-ScheduledTaskInfo $taskName).LastTaskResult -eq 267009) { Start-Sleep -Milliseconds 200; if ((Get-Date) -gt $timeout) { Write-Warning 'Skipping: Timeout'; break; }; }; if (($result = (Get-ScheduledTaskInfo $taskName).LastTaskResult) -ne 0) { Write-Error "^""Failed, due to exit code: $result."^""; } } finally { schtasks.exe /delete /tn $taskName /f | Out-Null; }; Get-Content $streamFile } finally { Remove-Item $streamFile, $scriptFile; }; }; $cmd = 'reg delete ''HKLM\Software\Microsoft\Windows Defender\SpyNet'' `'+"^""`r`n"^""+'        /v ''DisableBlockAtFirstSeen'' `'+"^""`r`n"^""+'        /f 2>$null'; Invoke-AsTrustedInstaller $cmd"

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