Notes about the QTN file extension:
To open this file type, a required software must be installed. Without it you only see a Windows message "The following file cannot be opened
" (Windows 7) or "How do you want to open this file?
" (Windows 10) if you double-click the file. There click on "More apps"
and choose a suitable software to view such files on your PC or from email attachments.
The QTN file type is primarily associated with 'Norman Virus Control' by Norman. An infected file is encrypted and given the .QTN extension. It is then stored in the \NVC\QARANTIN directory under the main Norman Virus Control directory.