You're here because you have a file that has a file extension ending in .ctf. Files with the file extension .ctf can only be launched by certain applications. It's possible that .ctf files are data files rather than documents or media, which means they're not meant to be viewed at all.

Files in the CTF format are classified as miscellaneous files and more specifically known as AVG update control files. These CTF files are affixed with the .ctf extension. The content stored in similar miscellaneous files by a wide variety of anti-virus and other system security applications to update its associated databases with definitions of certain malicious applications and to add definitions of newly discovered viruses and malware programs is also called an update control file, and these are the same features and specifications implemented into the content of a CTF file. The AVG Identity Protection software developed for Linux and Microsoft Windows-based systems can be installed to provide update support for the functionalities integrated into these CTF files. The AVG Anti-Virus 2012 application is another program that can be installed in a Microsoft Windows-based system or a computer running on Linux to implement support for the update functions stored in these CTF files. The AVG Internet Security 2012 software also has available versions intended for Microsoft Windows-based platforms and Linux systems, and this program can be used to access the data stored in a CTF file.

Launch a .ctf file, or any other file on your PC, by double-clicking it. If your file associations are set up correctly, the application that's meant to open your .ctf file will open it. It's possible you may need to download or purchase the correct application. It's also possible that you have the correct application on your PC, but .ctf files aren't yet associated with it. In this case, when you try to open a .ctf file, you can tell Windows which application is the correct one for that file. From then on, opening a  .ctf file will open the correct application. Click here to fix .ctf file association errors

Be careful not to rename the extension on .ctf files, or any other files. This will not change the file type. Only special conversion software can change a file from one file type to another.

A file extension is the set of three or four characters at the end of a filename; in this case, .ctf. File extensions tell you what type of file it is, and tell Windows what programs can open it. Windows often associates a default program to each file extension, so that when you double-click the file, the program launches automatically. When that program is no longer on your PC, you can sometimes get an error when you try to open the associated file.