One of our readers reported that all the file extensions have changed to some unknown file format. If so, it could be a virus! If a virus has changed all the files extensions to unknown applications, ...

A file extension is a suffix that is added to the end of a file name after a dot. It is usually two to four letters long. File extensions help Windows and other operating systems to know the standard ...

Microsoft hides file extensions in Windows by default even though it's a security risk that is commonly abused by phishing emails and malware distributors to trick people into opening malicious files.