Why you should change your KRBTGT password prior disabling RC4

While chilling on my couch, I stumbled over this pretty interesting Reddit thread: Story Time – How I blew up my company’s AD for 24 hours and fixed it : sysadmin (reddit.com)

Long story short: A poor guy applied some STIG hardening and his Active Directory blew up. Root cause was disabling RC4, which caused Kerberos failures, primarily documented by errors like “The encryption type requested is not supported by the KDC.” The guy fixed it by shutdown all domain controllers, changing the KRBTGT account password on one domain controller, and finally, everything came back

So why blew everything up after disabling RC4?… Read more

Use app-only authentication with the Microsoft Graph PowerShell SDK

In the previous blog post I have showed you how to interactively log in into the Microsoft Graph API. You had to enter a username, a password, and you had to enter a second factor. This is typically not want you want if you want to automate things. But there is another way to get access to the Microsoft Graph API.

Create an app registration

To get access, you have to register an app in your AzureAD. Go to your Azure portal and select “App registration” from the “Manage” section. Add a new registration by clicking to “New registration”.

Give your registration a meaningful name.… Read more

Getting started with the Microsoft Graph PowerShell SDK

There is a new API in town… naa, not really new, but the Microsoft Graph API will replace most, if not all, other Azure AD/ Microsoft 365 APIs. Actually, Microsoft has planned to retire Azure AD Graph API and ADAL in Juni 2022. Now they have postponed this date to somewhere after December 2022. This will give you some extra time to refactor your PowerShell scrips and move them to use the PowerShell SDK for Graph.

What is Microsoft Graph? Microsoft Graph is the spider web that connects everything in Microsoft 365. One part of Graph is a single and unified API endpoint, which allows you to access and manage Azure AD and Microsoft 365 services, such as Teams and Exchange Online, Intune etc.… Read more

Microsoft rolls back decision to block Office macros by default

Scrolling through my Twitter timeline is a common task to start my day. This morning, a tweet from @BleepinComputer has caught my attention.

My first reaction: WHAT. THE. FUCK?! Microsoft added this as feature 88883 in februrary 2022 to the Microsoft 365 roadmap, and I was pretty happy about this feature. Let’s take a look at this change.

The intention for this change was to add an extra layer of security in case that a user tried to open a downloaded file or an email attachment.… Read more

Wartungsfenster Podcast

Ausnahmsweise ein Blogpost in deutscher Sprache. Grund dafür ist, dass Claudia Kühn und ich seit Januar 2022 einen gemeinsamen Podcast rund um den Themenkomplex Datacenter, Cloud und IT ein. Eine lockere Kaminzimmerrunde in der wir entspannt über unseren Job, und alles was damit zu tun hat, plaudern.

Der Podcast erscheint alle zwei Wochen auf den üblichen Kanälen, oder ihr schaut auf der Homepage des Podcasts vorbei. Lasst gernen einen Kommentar/ Feedback da, und gebt uns eine Bewertung auf iTunes.… Read more

Upgrade to ESXi 7.0: Missing dependencies VIBs Error

This error gets me from time to time, regardless which server vendor, mostly on hosts that were upgraded a couple of times. In this case it was a ESXi host currently running a pretty old build of ESXi 6.7 U3 and my job was the upgrade to 7.0 Update 3c.

If you add a upgrade baseline to the cluster or host, and you try to remediate the host, the task fails with a dependency error. When taking a closer look into the taks details, you were getting told that the task has failed because of a failed dependency, but not which VIB it caused.

You can find the name if the causing VIB on the update manager tab of the host which you tried to update.… Read more

Mail notification for specific Active Directory security events

A customer used PRTG Network Monitor to notify him in case of account lockouts. This worked quite well until we implemented Admin Tiering. In order to get a mail notification in case of an account lockout, or other security-relevant events in Active Directory, I customized some scripts from my PowerShell dump.

The solution is pretty simple: I used the Task Planner to run a PowerShell script if a specific event id occurs. The events are generated in case of a various number of Active Directory events. You have to enable audit policy to get the needed events in the security event log. Take a look at Microsoft audit policy recommendations and enable what you need.… Read more

Outlook Web Access fails with “440 Login Timeout”

Today I faced an interesting problem. A customer told me that their Exchange 2010, which is currently part of a Exchange cross-forest migration project, has an issue with Outlook Web Access and the Exchange Control Panel. Both web sites fail with a white screen and a single message:

440 Login Timeout

I checked some basics, like certificate, configuration of the virtual directories and I found nothing suspicious. Most hints on the internet pointed towards problems with the IUSR_servername user, which is not used with IIS 7 and later. But authentication configuration and filesystem permissions were okay.… Read more

Modify ProxyAddresses of Office 365 users without Exchange Online

As part of a Office 365 tenant rebuild, I had to move a custom domain to the new Office 365 tenant. The old tenant was not needed anymore, and the customer had to move to a Non-Profit tenant for compliance reasons. So the migration itself was no big deal:

  • disable AzureAD sync
  • change UPN of all users
  • remove the domain
  • connect the domain to the new tenant
  • setup a new AzureAD sync
  • assign licenses
  • time for a beer

That was my, honestly, naive plan for this migration.

Image by Gerd Altmann from Pixabay 

Disabling the AzureAD sync was easy. Even the change from ADFS to Password Hash Sync was easy. Changing the UPN for all users was a bit challenging, but the PowerSHell code in this article was quite helpful.… Read more

Escaping special characters in proxy auth passwords in vCenter

EDIT: It seems that his was fixed in vCenter 7.0 U3.

While debugging a vCener Lifecycle Manager, which was unable to download updates, I’ve stumbled over a weird behaviour, which is (IMHO) by design.

Some of you might use a proxy server. And some of you might use a proxy server which requires credentials. In my case, my customer uses a Sophos SG appliance as a web proxy server with authentication. The customer creaded a user with a complex password. But I was unable to get a working internet connection.

Image by Ed Webster from Pixabay 

I played a bit with curl on the bash of the vCenter.… Read more