Because Windows might hide the .exe extension, the user only sees GreatVideo.mp4 .

.mp4 and .mkv are both video containers. There is no legitimate reason to stack them consecutively in a single file name.

Go to your operating system folder settings and uncheck the option that says "Hide extensions for known file types." This ensures you always see the actual final extension.

If a file has a video extension like .mp4 but displays a generic application icon instead of a video thumbnail, do not open it.

The most dangerous application of this naming convention occurs when attackers hide executable files behind harmless media extensions.

Even if this specific file is just a poorly named video rather than a virus, its structure indicates severe handling issues:

The filename is a classic example of a double extension used to mask the true identity of a computer file. This technique is frequently utilized by bad actors to trick users into running malicious scripts or downloading unwanted software. 🛡️ Why File Extensions Matter

Every file on your computer has a file extension—a suffix consisting of a period followed by a few letters (like .jpg , .pdf , or .mp4 ). This extension tells your operating system which program should be used to open the file.