RDP login error and Lan Manager authentication levels

When trying to connect to certain hardened Windows VMs using RDP Client the VM might continually ask you for username and password at the login and show that the login attempt failed. Even though you know the login creds are correct.


This is generally down to the LAN Manager authentication level setting on the hardened image. To successfully connect you will need to configure a comparable security setting on your own Microsoft  OS as the destination OS. This will require you to login into the VM via a Console session if the O/S has been virtualised to confirm the setting.  To check or change  the authentication level use this

  1. Go to Start – Run and type in gpedit.msc
  2. Navigate to Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options
  3. In there, double click on Network security: Lan Manager authentication level


Some more information on Lan Manager Authentication Levels can be found here.

Here is a table from the same website showing the different setting and their associated security level.



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