Open MUI File

What is a MUICache?

MUI, or Multilanguage User Interface, is an internationalization technology used by Windows operating systems versions 2000 and later. Files with the MUI extension contain resources that allow the Windows interface to display different languages. The Windows operating system can open .MUI files, depending on the instruction given to the operating system by the user.

With these files it is possible for the user to switch the languages without changing the binaries of the operating system kernel and using them in more than one language. Languages are applied as packages and contain the necessary resources to localize part or all of the user interface.

MUI files generate a key in the Windows registry that we will briefly explain in the following lines.

MUICache

MUICache is a windows resource that acts as a registry key that is responsible for storing information about the executable of each application and that the operating system automatically extracts when a new application is used.

MUICache has the feature that even if you delete some elements, they will reappear the next time you run that application.

The location of the MUICache data in the registry prior to Windows Vista is:

HKEY_CURRENT_USER\Software\Microsoft\Windows\ShellNoRoam\MUICache.

Starting with Windows Vista, MUICache data is stored in

HKEY_CURRENT_USER\Software\Classes\Local\Settings\Software\Microsoft\Windows\Shell\MuiCache

MUICache and Malwares

It should be noted that MUICache is a very common registry key to be attacked by malware, Trojans and the like. There are references to malwares that create values in this key, specifically Trojan-Alexmo and Adware-BlowSearch.

The indications lead to the keys being created, however they did not give more information about their use. The most notable recommendation is that you should keep your antispyware up-to-date and do full system scans very regularly.

It is known that some recognized antivirus such as Panda Antivirus, have detected some malware that masquerades as "antivirus" and uses MUICache to save temporary files, in case they are eliminated by a real antivirus.