account

Reset or Remove the Windows Hello PIN

Windows 10 offers various ways to logon to your device. All of them have their pro’s and con’s. One thing is for sure, Microsoft loves the Windows Hello PIN. Even on an Active Directory Domain joined system – if you want to e.g. set up a Finger-Print login, you will be forced to generate a Windows Hello PIN, at least by default.

Funnily it can happen that you don’t even have the option to reset the PIN. What if the user forgot his PIN? No big deal? Well… it actually is a big deal. By default Windows goes back to the PIN if the Finger-Print reader does not work, what is especially common with the Microsoft Surface Keyboards, sure you can rip them off and re-attach to make it work again, but still your user-base / employee-base will say it asks for a PIN and I forgot it..

Fingerprints and PINs are stored locally on the device, in a secured vault. You can’t really alter it, but you can remove it.

In order to remove all locally stored PINs and possibly even Finger-Prints, you must delete all contents of %windir%\ServiceProfiles\LocalService\AppData\Local\Microsoft\NGC.

The quickest way to accomplish this is using the two following commands in an elevated Command Prompt / CMD (run as administrator).

takeown /f %windir%\ServiceProfiles\LocalService\AppData\Local\Microsoft\NGC /r /d y

icacls %windir%\ServiceProfiles\LocalService\AppData\Local\Microsoft\NGC /grant administrators:F /t

takeown /f %windir%\ServiceProfiles\LocalService\AppData\Local\Microsoft\NGC /r /d y

icacls %windir%\ServiceProfiles\LocalService\AppData\Local\Microsoft\NGC /grant administrators:F /t

The first one will take ownership of the folder, the second one then will grant administrators rights to it.

Once this is done, you need to delete all contents of the folder. If you are logged on as an administrator you can just use Windows Explorer. If you are logged on as a regular user, you need to do it either more manual in CMD or use e.g. a tool like 7-zip in elevated mode and navigate to the folder, be aware that 7-zip might not be able to handle %windir%, either navigate manually to the folder or use C:\Windows\ServiceProfiles\LocalService\AppData\Local\Microsoft\NGC to get to the path. Delete all contents.

Reboot.

This sledgehammer method will delete all stored PINs and other information for all accounts known by the device. They will need to logon with their Active Directory password and start from scratch. You might also need to click on e.g. REMOVE in the Finger-Print configuration to start over.

Monitor group memberships in Active Directory with PRTG

There is at least one group you want to monitor for any membership changes in Active Directory / LDAP – the Domain Admins group. This is so important, as any changes to this group could cause great harm to your whole system. Of course there are other ways in but you for sure want to monitor at least the basic information of the amount of users in this group.

In order to do so, I wrote a PowerShell script that provides you the amount of members of any given group in Active Directory, as well as a text response (under the probe name and in some alerts if activated) of the sAMAccountName of each member in the group. This way you can hopefully right away determine the changed object, assuming you know what should be in there and what not.

If you have nested groups, you might wanna monitor them as well till you reach a user only level.

Create the script as always on your PRTG probing server in C:\Program Files (x86)\PRTG Network Monitor\Custom Sensors\EXEXML and add a new EXE/Advanced XML sensor in PRTG. Select the script and provide at a bare minimum the parameter MonitoredGroup.

Parameter samples:

-MonitoredGroup “Domain Admins”
-MonitoredGroup “Domain Admins” -Server “MyDC.domain.local”

If you do not provide a server name, the system will try determine it on it’s own – default Domain-Membership etc..

Once the first run was successful you should review the results and set the upper and lower error limit on the PRTG sensor to the current amount of members. Any change then will cause the sensor to go in to error status and inform you therefor about the change.

param(
	[string]$Server = "",
	[string]$MonitoredGroup = ""
)
Import-Module ActiveDirectory

If ($Server.Length -gt 0) {
    $LDAPGroup = Get-ADGroupMember $MonitoredGroup -Server $Server
} Else {
    $LDAPGroup = Get-ADGroupMember $MonitoredGroup 
}

[string]$LDAPGroupMembers = ""
Foreach ($Member in $LDAPGroup){
    If ($LDAPGroupMembers.Length -gt 0) {$LDAPGroupMembers += ", "}
    $LDAPGroupMembers += $Member.SamAccountName
}

$XML = "<prtg>
            <result>
                <channel>Amound of Users in Group</channel>
                <value>"+ $LDAPGroup.count +"</value>
            </result>			
            <text>"+ $MonitoredGroup +" Members: " + $LDAPGroupMembers + "</text>
        </prtg>"
 
Function WriteXmlToScreen ([xml]$XML) #just to make it clean XML code...
{
	$StringWriter = New-Object System.IO.StringWriter;
	$XmlWriter = New-Object System.Xml.XmlTextWriter $StringWriter;
	$XmlWriter.Formatting = "indented";
	$xml.WriteTo($XmlWriter);
	$XmlWriter.Flush();
	$StringWriter.Flush();
	Write-Output $StringWriter.ToString();
}
 
WriteXmlToScreen $XML;

param(

[string]$Server = "",

[string]$MonitoredGroup = ""

)

Import-Module ActiveDirectory

If ($Server.Length -gt 0) {

$LDAPGroup = Get-ADGroupMember $MonitoredGroup -Server $Server

} Else {

$LDAPGroup = Get-ADGroupMember $MonitoredGroup

}

[string]$LDAPGroupMembers = ""

Foreach ($Member in $LDAPGroup){

If ($LDAPGroupMembers.Length -gt 0) {$LDAPGroupMembers += ", "}

$LDAPGroupMembers += $Member.SamAccountName

}

$XML = "<prtg>

<channel>Amound of Users in Group</channel>

<value>"+ $LDAPGroup.count +"</value>

</result>

<text>"+ $MonitoredGroup +" Members: " + $LDAPGroupMembers + "</text>

</prtg>"

Function WriteXmlToScreen ([xml]$XML) #just to make it clean XML code...

{

$StringWriter = New-Object System.IO.StringWriter;

$XmlWriter = New-Object System.Xml.XmlTextWriter $StringWriter;

$XmlWriter.Formatting = "indented";

$xml.WriteTo($XmlWriter);

$XmlWriter.Flush();

$StringWriter.Flush();

Write-Output $StringWriter.ToString();

}

WriteXmlToScreen $XML;

October 13, 2020 by Florian Rossmark monitoring prtg scripts security server

Amount of locked out accounts

It is a good to know how many of your user accounts are locked out right now… I would go as far as saying you should monitor this and have alert levels on it, cause this could indicate and reveal a brute-force like attack against your system.

Doing it manually in a PowerShell (assuming you have RSAT / Active-Directory PowerShell modules installed) can be done with the following command that will show you who is locked out and the calculated amount as well..

$s=Search-ADAccount -LockedOut |ft
$s
'CurrentCount: ' + $s.count

$s=Search-ADAccount -LockedOut |ft

'CurrentCount: ' + $s.count

Using PRTG you can add the following advanced script

Import-module activedirectory
$Count=-1

$Accounts = Search-ADAccount -LockedOut
$Count=$Accounts.Count

$Users = ""
foreach ($user in $Accounts) {
	if ($Users.Length -gt 0) {
		$Users += " / "
	}
	$Users += $user.SamAccountName
}

$XML =  "<prtg>"
$XML += "<result><channel>LDAP accounts locked out</channel><value>$Count</value><unit>Count</unit></result>"
$XML += "<text>$Users</text>"
$XML += "</prtg>"

Function WriteXmlToScreen ([xml]$xml)
{
    $StringWriter = New-Object System.IO.StringWriter;
    $XmlWriter = New-Object System.Xml.XmlTextWriter $StringWriter;
    $XmlWriter.Formatting = "indented";
    $xml.WriteTo($XmlWriter);
    $XmlWriter.Flush();
    $StringWriter.Flush();
    Write-Output $StringWriter.ToString();
}

WriteXmlToScreen $XML

Import-module activedirectory

$Count=-1

$Accounts = Search-ADAccount -LockedOut

$Count=$Accounts.Count

$Users = ""

foreach ($user in $Accounts) {

if ($Users.Length -gt 0) {

$Users += " / "

}

$Users += $user.SamAccountName

}

$XML = "<prtg>"

$XML += "<result><channel>LDAP accounts locked out</channel><value>$Count</value><unit>Count</unit></result>"

$XML += "<text>$Users</text>"

$XML += "</prtg>"

Function WriteXmlToScreen ([xml]$xml)

{

$StringWriter = New-Object System.IO.StringWriter;

$XmlWriter = New-Object System.Xml.XmlTextWriter $StringWriter;

$XmlWriter.Formatting = "indented";

$xml.WriteTo($XmlWriter);

$XmlWriter.Flush();

$StringWriter.Flush();

Write-Output $StringWriter.ToString();

}

WriteXmlToScreen $XML

After adding it as a sensor, it will create a single channel with the amount of locked out users. You should set error limits:

minimum error limit: 0
- the script returns -1 if an error occurred
maximum error limit: this depends on your user base – I would say about 5% of your users – no more.. depends as well on the lockout-duration in your security policy…

The advantage of the script in PRTG is – it always reports back additional text – the currently locked out SamAccount names.. respective user-names.. so in case it generates an error – you will see some more information…

Assuming there is a brute-force, you might see this sparking and going down – meaning someone tries to find an entry account… since the lockout attribute causes an emergency-replication of your domain-controllers (this attribute bypasses the regular replication interval) you can fire it relatively simply against your domain, the script just uses the current logon domain of the executing user.

October 25, 2019 by Florian Rossmark monitoring prtg security server

Find user account lockout events

There are various ways and tools to tackle this – in the end it boils down to a few facts

account lockouts are logged per domain controller – to be more specific – only on the DC where the lockout happened
- this can be complicated in bigger environments
the lockout event 4771 does not necessarily reveal the initial reason – but it should give you enough information about where it occurred to further investigate

The manual way via Eventlog / Eventviewer in Windows on a DC

right click on the SECURITY eventlog
select Filter Current Log
go to the register card XML
check the box Edit query manually
Insert the XML code below – make sure you replace the USERNAMEHERE value with the actual username
1. no domain
2. exact username
3. NOT case sensitive

<QueryList>
  <Query Id="0" Path="Security">
    <Select Path="Security">*[System[(EventID=4771)]][EventData[Data[@Name='TargetUserName'] and (Data='USERNAMEHERE')]]</Select>
  </Query>
</QueryList>

<Select Path="Security">*[System[(EventID=4771)]][EventData[Data[@Name='TargetUserName'] and (Data='USERNAMEHERE')]]</Select>

</Query>

</QueryList>

This results in to a filtered eventlog view for the event id 4771 and the username you specified.

Using PowerShell to automate this

PowerShell can execute a script that would give you the same output – I wrote the script below. It expects at least the parameter UserName – see below for more information.

UserName
- this parameter is mandatory – the exact username without the domain, this is NOT case sensitive
DomainController
- specify this to narrow it down to a single DC – otherwise all domain controllers will be contacted (might take a while)
FullDetails
- set it to $true if you want to see details – otherwise you get only the table format
Example
- Find-AccountLockoutOnDCForUser.ps1 -FullDetails $true -UserName JDoe

param(
    [string] $DomainController = "",
    [string] $UserName = "",
    [bool]   $FullDetails = $false
)

$Query = @"
<QueryList>
    <Query Id="0" Path="Security">
    <Select Path="Security">*[System[(EventID=4771)]][EventData[Data[@Name='TargetUserName'] and (Data='$UserName')]]</Select>
  </Query>
</QueryList>
"@

If ($DomainController.Length -eq 0) {
    Import-Module ActiveDirectory
    $DomainControllers = Get-ADDomainController -Filter * | Select-Object -ExpandProperty Name
    ForEach($DC In $DomainControllers) {
        Write-Host "checking DC: $DC"
        If ($FullDetails) {
            Get-WinEvent -ComputerName $DC -FilterXml $Query -ErrorAction SilentlyContinue | fl
        } Else {
            Get-WinEvent -ComputerName $DC -FilterXml $Query -ErrorAction SilentlyContinue | ft
        }
    }
} Else {
    If ($FullDetails) {
        Get-WinEvent -ComputerName $DomainController -FilterXml $Query -ErrorAction SilentlyContinue | fl
    } Else {
        Get-WinEvent -ComputerName $DomainController -FilterXml $Query -ErrorAction SilentlyContinue | ft
    }
}

param(

[string] $DomainController = "",

[string] $UserName = "",

[bool] $FullDetails = $false

)

$Query = @"

<Select Path="Security">*[System[(EventID=4771)]][EventData[Data[@Name='TargetUserName'] and (Data='$UserName')]]</Select>

</Query>

</QueryList>

If ($DomainController.Length -eq 0) {

Import-Module ActiveDirectory

$DomainControllers = Get-ADDomainController -Filter * | Select-Object -ExpandProperty Name

ForEach($DC In $DomainControllers) {

Write-Host "checking DC: $DC"

If ($FullDetails) {

Get-WinEvent -ComputerName $DC -FilterXml $Query -ErrorAction SilentlyContinue | fl

} Else {

Get-WinEvent -ComputerName $DC -FilterXml $Query -ErrorAction SilentlyContinue | ft

}

} Else {

If ($FullDetails) {

Get-WinEvent -ComputerName $DomainController -FilterXml $Query -ErrorAction SilentlyContinue | fl

} Else {

Get-WinEvent -ComputerName $DomainController -FilterXml $Query -ErrorAction SilentlyContinue | ft

}

February 20, 2019 by Florian Rossmark scripts security server

account

Reset or Remove the Windows Hello PIN

Monitor group memberships in Active Directory with PRTG

Amount of locked out accounts

Find user account lockout events

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