QUA file extension is used by Avira antivirus software. QUA files stores viruses quarantined by the antivirus tool, which prevents malicious files from activating on the system.

Special file folder is used to store quarantied infected files with added QUA extension. QUA files are creates in situations when the program for some reason cannot delete virus from as infected file. When the software download and update that can help clean the infected file, it removes the virus and restores the file. Files in quarantine folder can be manually deleted by the user.