windows-hardening – Security skill for AI agents

Windows Hardening

Secure Windows servers following Microsoft security baselines and CIS benchmarks.

Prerequisites

• Windows Server 2019 or later (2022 recommended)
• Only the least privilege required for the approved host/policy; Domain Admin is not a default prerequisite.
• PowerShell 5.1+ (built into Windows Server)
• Group Policy Management Console for domain environments
• Microsoft Security Compliance Toolkit (recommended)

Security Baseline Deployment

# Download and apply Microsoft Security Baseline
# Download from: https://www.microsoft.com/en-us/download/details.aspx?id=55319

# These optional community DSC modules are not the Security Compliance Toolkit; review publisher/version before separate installation.
Install-Module -Name SecurityPolicyDsc -Force
Install-Module -Name AuditPolicyDsc -Force
Install-Module -Name PSDesiredStateConfiguration -Force

# Import and apply a security baseline GPO (from Security Compliance Toolkit)
# Extract the toolkit, then:
# LGPO.exe is an executable, not a PowerShell module. Verify the downloaded Microsoft binary signature and version.

# Apply local group policy from baseline
.\LGPO.exe /g ".\GPO\{baseline-gpo-guid}"

# Export current security policy for review
secedit /export /cfg C:\SecurityAudit\current-policy.inf

Account Policies

# ============================================
# Password Policy Configuration
# ============================================

# Set password policy via net accounts
# Example local-account settings only; align password expiry with current approved policy rather than blanket 90-day rotation.
net accounts /minpwlen:14 /minpwage:1 /uniquepw:24

# Or configure via PowerShell DSC
Configuration PasswordPolicy {
    Import-DscResource -ModuleName SecurityPolicyDsc

    Node localhost {
        AccountPolicy PasswordPolicy {
            Name                                = "PasswordPolicy"
            Minimum_Password_Length              = 14
            Maximum_Password_Age                = 0  # illustrative no periodic expiry; current baseline/incident policy governs
            Minimum_Password_Age                = 1
            Enforce_password_history             = 24
            Password_must_meet_complexity_requirements = "Enabled"
            Store_passwords_using_reversible_encryption = "Disabled"
        }
    }
}

# ============================================
# Account Lockout Policy
# ============================================
net accounts /lockoutthreshold:5 /lockoutwindow:30 /lockoutduration:30

# ============================================
# User Account Hardening
# ============================================

# Rename and disable default accounts
Rename-LocalUser -Name "Administrator" -NewName "LocalAdmin"
Disable-LocalUser -Name "Guest"
Disable-LocalUser -Name "DefaultAccount"

# Remove unnecessary local accounts
$unnecessaryAccounts = Get-LocalUser | Where-Object {
    $_.Enabled -eq $true -and
    $_.Name -notin @("LocalAdmin", "SYSTEM", "NetworkService", "LocalService")
}
foreach ($account in $unnecessaryAccounts) {
    Write-Host "Review account: $($account.Name) - Last logon: $($account.LastLogon)"
}

# Configure Local Administrator Password Solution (LAPS)
# Legacy Microsoft LAPS example only: RSAT-AD-PowerShell does not install AdmPwd.PS.
# Prefer built-in Windows LAPS with its current schema/permissions/backup policy; do not mix legacy and modern commands.
Import-Module AdmPwd.PS  # only when legacy LAPS was intentionally installed and remains supported

# Configure LAPS for the OU
Set-AdmPwdComputerSelfPermission -OrgUnit "OU=Servers,DC=example,DC=com"
Set-AdmPwdReadPasswordPermission -OrgUnit "OU=Servers,DC=example,DC=com" -AllowedPrincipals "Domain Admins"

Group Policy Security Settings

# ============================================
# User Rights Assignment (via GPO or local policy)
# ============================================

# Restrict remote desktop access
# Computer Configuration > Policies > Windows Settings > Security Settings > Local Policies > User Rights Assignment
# "Allow log on through Remote Desktop Services" = Administrators, Remote Desktop Users

# Deny log on locally for service accounts
# "Deny log on locally" = Service accounts

# Configure via registry (alternative to GPO)
# Restrict anonymous enumeration of SAM accounts
Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Lsa" `
    -Name "RestrictAnonymousSAM" -Value 1

# Restrict anonymous enumeration of shares
Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Lsa" `
    -Name "RestrictAnonymous" -Value 1

# Do not display last user name
Set-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System" `
    -Name "DontDisplayLastUserName" -Value 1

# ============================================
# Security Options
# ============================================

# Disable SMBv1 (critical security hardening)
Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol -NoRestart
Set-SmbServerConfiguration -EnableSMB1Protocol $false -Force

# Require SMB signing
Set-SmbServerConfiguration -RequireSecuritySignature $true -Force
Set-SmbClientConfiguration -RequireSecuritySignature $true -Force

# Disable LLMNR (prevent credential theft)
New-Item -Path "HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\DNSClient" -Force
Set-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\DNSClient" `
    -Name "EnableMulticast" -Value 0

# Disable NetBIOS over TCP/IP
$adapters = Get-WmiObject Win32_NetworkAdapterConfiguration | Where-Object { $_.IPEnabled -eq $true }
foreach ($adapter in $adapters) {
    $adapter.SetTcpipNetbios(2)  # 2 = Disable
}

# Disable WDigest (prevent plaintext password caching)
Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProviders\WDigest" `
    -Name "UseLogonCredential" -Value 0

# Enable LSA Protection
Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Lsa" `
    -Name "RunAsPPL" -Value 1

# Configure UAC
Set-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System" `
    -Name "EnableLUA" -Value 1
Set-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System" `
    -Name "ConsentPromptBehaviorAdmin" -Value 2
Set-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System" `
    -Name "PromptOnSecureDesktop" -Value 1

Windows Firewall Configuration

# ============================================
# Enable Windows Firewall on all profiles
# ============================================
Set-NetFirewallProfile -Profile Domain,Public,Private -Enabled True

# Default deny inbound, allow outbound
Set-NetFirewallProfile -Profile Domain -DefaultInboundAction Block -DefaultOutboundAction Allow
Set-NetFirewallProfile -Profile Public -DefaultInboundAction Block -DefaultOutboundAction Allow
Set-NetFirewallProfile -Profile Private -DefaultInboundAction Block -DefaultOutboundAction Allow

# Enable logging
Set-NetFirewallProfile -Profile Domain -LogAllowed True -LogBlocked True `
    -LogFileName "%SystemRoot%\System32\LogFiles\Firewall\pfirewall.log" `
    -LogMaxSizeKilobytes 32768

# ============================================
# Inbound Rules
# ============================================

# Allow RDP from management network only
New-NetFirewallRule -DisplayName "Allow RDP - Management" `
    -Direction Inbound -Protocol TCP -LocalPort 3389 `
    -RemoteAddress 10.0.100.0/24 -Action Allow -Profile Domain

# Allow WinRM from management network
New-NetFirewallRule -DisplayName "Allow WinRM - Management" `
    -Direction Inbound -Protocol TCP -LocalPort 5985,5986 `
    -RemoteAddress 10.0.100.0/24 -Action Allow -Profile Domain

# Allow ICMP from internal networks
New-NetFirewallRule -DisplayName "Allow ICMP - Internal" `
    -Direction Inbound -Protocol ICMPv4 -IcmpType 8 `
    -RemoteAddress 10.0.0.0/8 -Action Allow

# Allow specific application
New-NetFirewallRule -DisplayName "Allow IIS HTTPS" `
    -Direction Inbound -Protocol TCP -LocalPort 443 `
    -Action Allow -Profile Domain,Private

# Block all other inbound by default (already set above)

# ============================================
# Outbound Rules (optional - restrict egress)
# ============================================

# Allow DNS
New-NetFirewallRule -DisplayName "Allow DNS" `
    -Direction Outbound -Protocol UDP -RemotePort 53 `
    -Action Allow

# Allow HTTPS for updates
New-NetFirewallRule -DisplayName "Allow HTTPS Out" `
    -Direction Outbound -Protocol TCP -RemotePort 443 `
    -Action Allow

# Allow NTP
New-NetFirewallRule -DisplayName "Allow NTP" `
    -Direction Outbound -Protocol UDP -RemotePort 123 `
    -Action Allow

# ============================================
# Firewall Audit
# ============================================

# List all enabled firewall rules
Get-NetFirewallRule -Enabled True | Format-Table Displ

… (full content is in the download package)