Windows 10: Clear all credentials for "Access work or school"

zatireszatires · Aug 19, 2021

Hi,I am referencing "Access work or school" in the settings menu on a shared computer.I need to know how to clear all the credentials using a batch file during login or disable people from saving them in this computer.I leave the computer switched on for a month and there are 100 over entries in there I clear those every month so please do not tell me to manually remove those entries.Help would be appreciated,Zac

:)

amimandami · Aug 19, 2021

Cannot clear network access credentials

OS: Windows 10 x64

I access a network server using a username + password. I'd like to use another username+password, but I cannot clear the old credentials. What I've done until now:

there was nothing to delete in Windows credentials (Control Panel\All Control Panel Items\Credential Manager)

net use * /del

klist purge

restart explorer

restart PC

changed the password on the server, and saving NEW credentials on the PC. When I reverted back to original server password, the PC connected automatically (this makes me think that those credentials were saved somewhere, but I don't know where).

MarcinMrowiec · Aug 19, 2021

Scheduled tasks run with elevated privileges can't access stored Windows credentials

It seems that after Creators update scheduled tasks run with elevated privileges ('run with highest privileges' option) can't access stored Windows credentials. Is that a bug or an intentional change and is there a recommended workaround?

Here's one way to reproduce the behaviour:

Start Credential Manger and add some Windows share credentials.

In a console window type 'cmdkey /list', which should list the added credentials

Create a task in a task manager:

Trigger: on user logon

Action: run cmd.exe

Tick the 'run with highest privileges' option

Reboot the machine and log in

In the console window (let's call it 'console 1') opened from the scheduled task type 'cmdkey /list'. This most likely won't display the credentials added in step 1 and properly listed in step 2. ->
This looks like a bug

Now, without closing 'console 1' open another console window as an administrator (let's call it 'console 2') and type 'cmdkey /list'. This will properly list credentials added in step 1.

Switch to 'console 1' and type 'cmdkey /list' again. This time the credentials are listed properly, unlike in step 5. It looks like an access to Windows credentials was somehow 'unlocked' by step 6.

Brink · Aug 19, 2021

Credential Guard lab companion

If you have heard about Credential Guard in Windows Server 2016 (and in Windows 10), but do not have an environment to try it out, here is a lab environment we built for you to play.

Lab access

The link will lead you to a sign up page, after that, you will see the following labs listed for Windows Server 2016:

Windows Server 2016 labs

There are 3 exercises in the “Implementing Breach Resistance Security in Windows Server 2016”:

Credential Guard

Remote Credential Guard

Device Guard

This blogpost will walk you through the Credential Guard lab details.

After click on the link of Breach Resistance lab, you be required to sign in and then you can launch the lab:

Sign-in

Launch page

It takes a few minutes to create the VMs, and once it has done, you will see the following machines prepared:

Initialize

DC: domain controller, which is not used for this exercise.

SRV01 and SRV02: both are Windows Server 2016, and used for the lab exercise.

Lab exercise – Explained

The steps are listed in the Content section:

Content

This lab is structured to cover the following in sequence:

Understand how attackers can use the hash in memory to gain access to domain controllers

Configure Credential Guard

Verify the hash in memory is protected using Credential Guard

You can follow the steps listed under the content section to complete the lab, the intent of the blog, is to break the procedures into groups, to help you understand the exercise better.

Prep the hash

Lsass.exe is the process which handles user logon, it stores the user credential information in its memory. The memory is cleared when the machine starts up. In this lab environment, all the virtual machines start at the time lab launches, when you logon to the machine, you will only have the logon user credential information in memory. In order to demonstrate an attacker gaining user access using other account’s hash, the first part of the lab is to simulate a server which has been running for a while, different users had remotely or locally connected to it, therefore, lsass memory stored many different user credential information.
This is accomplished by step 1-8.

Retrieving credential hash

Mimikatz is a popular tool for retrieving lsass memory information. The tool has been copied to the lab machines, step 9-13 walk you through the process of dumping lsass memory using Mimikatz.

Pass the Hash

Pass the hash is a hacking technique that allows an attacker to authenticate by using the underlying NTLM, instead of specifying the user password. In step 14 to 24, you will extract LabAdmin hash from lsass using Mimikatz, and use the hash to open a PowerShell console, and perform a couple of operations using the LabAdmin privilege:

Add a user to the domain admin group

Open remote PowerShell connection to a domain controller

Both operations could not be performed by the logon user. But using the hash of the LabAdmin, an attacker will be able to do it using the information retrieve from Lsass memory.

Configure and verify Credential Guard

Step 25 to 36 illustrate the steps to configure credential guard, then verify its status using msinfo32.exe and PowerShell.

Step 37 to 43 goes further to use Mimikatz to show the hash in Lsass is now encrypted using Credential Guard.

More info

The exercise illustrated the benefit of Credential Guard in Windows Server 2016 as well as Windows 10. For more information, you can find here.
Click to expand...

Source: Credential Guard lab companion Datacenter and Private Cloud Security Blog

See also:

Enable or Disable Credential Guard in Windows 10 Windows 10 Security System Tutorials

Verify if Credential Guard is Enabled or Disabled in Windows 10 Windows 10 Security System Tutorials

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