Windows Explorer: display of known file type extensions is disabled
Malicious software often masks its executable file by giving it the appearance of popular file formats (documents, images, music, movies, etc.), replacing the icons for these categories. When display of a known type of file extensions is disabled, the file "image.jpg__________.exe" appears to the user as "image...". Thus, the user can run a malicious program that allows an intruder to gain control over the system and user data.