Modify Local Security Policy using Powershell

There is no pure powershell way of doing it as per @Kayasax's answer, you have to wrap secedit into Powershell.

secedit /export /cfg c:\secpol.cfg
(gc C:\secpol.cfg).replace("PasswordComplexity = 1", "PasswordComplexity = 0") | Out-File C:\secpol.cfg
secedit /configure /db c:\windows\security\local.sdb /cfg c:\secpol.cfg /areas SECURITYPOLICY
rm -force c:\secpol.cfg -confirm:$false

I use Windows 7

I have solved it by using the following powershell script

$name = $PSScriptRoot + "\" + $MyInvocation.MyCommand.Name

if (!([Security.Principal.WindowsPrincipal][Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole] "Administrator")) { Start-Process powershell.exe "-NoProfile -ExecutionPolicy Bypass -File `"$name`"" -Verb RunAs; exit }

$registryPath = "HKLM:\SYSTEM\CurrentControlSet\Control\Lsa"

$Name = "LimitBlankPasswordUse"

$value = "0"

New-ItemProperty -Path $registryPath -Name $name -Value $value ` -PropertyType DWORD -Force | Out-Null

This script will automatically run as admin, if not already opened in admin mode

I Also tried the script Raf wrote. I had version 2.0, but I only got it to work with version 4.0

I decided to write a couple functions to make this process easier.

Parse-SecPol : will turn Local Security Policy into a PsObject. You can view all the properties and make changed to the object.

Set-SecPol : will turn the Parse-SecPol object back into a config file and import it to into the Local Security Policy.

Here is a example of its usage :

Function Parse-SecPol($CfgFile){ 
    secedit /export /cfg "$CfgFile" | out-null
    $obj = New-Object psobject
    $index = 0
    $contents = Get-Content $CfgFile -raw
    [regex]::Matches($contents,"(?<=\[)(.*)(?=\])") | %{
        $title = $_
        [regex]::Matches($contents,"(?<=\]).*?((?=\[)|(\Z))", [System.Text.RegularExpressions.RegexOptions]::Singleline)[$index] | %{
            $section = new-object psobject
            $_.value -split "\r\n" | ?{$_.length -gt 0} | %{
                $value = [regex]::Match($_,"(?<=\=).*").value
                $name = [regex]::Match($_,".*(?=\=)").value
                $section | add-member -MemberType NoteProperty -Name $name.tostring().trim() -Value $value.tostring().trim() -ErrorAction SilentlyContinue | out-null
            }
            $obj | Add-Member -MemberType NoteProperty -Name $title -Value $section
        }
        $index += 1
    }
    return $obj
}

Function Set-SecPol($Object, $CfgFile){
   $SecPool.psobject.Properties.GetEnumerator() | %{
        "[$($_.Name)]"
        $_.Value | %{
            $_.psobject.Properties.GetEnumerator() | %{
                "$($_.Name)=$($_.Value)"
            }
        }
    } | out-file $CfgFile -ErrorAction Stop
    secedit /configure /db c:\windows\security\local.sdb /cfg "$CfgFile" /areas SECURITYPOLICY
}


$SecPool = Parse-SecPol -CfgFile C:\test\Test.cgf
$SecPool.'System Access'.PasswordComplexity = 1
$SecPool.'System Access'.MinimumPasswordLength = 8
$SecPool.'System Access'.MaximumPasswordAge = 60

Set-SecPol -Object $SecPool -CfgFile C:\Test\Test.cfg