#Requires -RunAsAdministrator

<#
.SYNOPSIS
    Configures static DNS server addresses on active network adapters.

.DESCRIPTION
    This script retrieves all active (connected) network interfaces on the endpoint and assigns 
    primary DNS (Quad9) and secondary backup DNS (Cloudflare) servers.

.NOTES
    Created:     2025-03-02
    Modified:    2026-10-04
    
    DNS Server Mappings:
      - Quad9 Primary:   9.9.9.9        (Malware blocking + DNSSEC)
      - Quad9 Secondary: 149.112.112.11 (Malware blocking + DNSSEC)
      - Cloudflare Prim: 1.1.1.2        (Malware blocking) 
      - Cloudflare Sec:  1.0.0.2        (Malware blocking)
      
      * Note: If adult content blocking is also desired via Cloudflare, 
        use 1.1.1.3 and 1.0.0.3 instead.
#>

[CmdletBinding(SupportsShouldProcess = $true)]
param (
    # Array of DNS IPv4 addresses in priority order
    [string[]]$DnsServers = @("9.9.9.9", "149.112.112.11", "1.1.1.2", "1.0.0.2")
)

# 1. Retrieve active/connected network adapters (filters out disabled, virtual, or disconnected NICs)
$ActiveAdapters = Get-NetAdapter | Where-Object { $_.Status -eq 'Up' }

if (-not $ActiveAdapters) {
    Write-Warning "No active network adapters found on this endpoint."
    return
}

# 2. Apply DNS settings to each active interface
foreach ($Adapter in $ActiveAdapters) {
    
    $InterfaceName  = $Adapter.Name
    $InterfaceIndex = $Adapter.InterfaceIndex

    if ($PSCmdlet.ShouldProcess("Interface: $InterfaceName (Index: $InterfaceIndex)", "Set DNS servers to $($DnsServers -join ', ')")) {
        try {
            # Set the static DNS client addresses
            Set-DnsClientServerAddress -InterfaceIndex $InterfaceIndex -ServerAddresses $DnsServers -ErrorAction Stop
            
            Write-Host "Successfully updated DNS for '$InterfaceName' (Index: $InterfaceIndex)" -ForegroundColor Green
        }
        catch {
            Write-Error "Failed to update DNS on interface '$InterfaceName' (Index: $InterfaceIndex). Error: $_"
        }
    }
}