madoka.exe, mostly known as the Ghost virus or the Sadako virus in Japan, is a japanese Joke program, which is a variant of the Win32/FlaGhost Malware. When the user runs the program, a picture of a japanese woman in full-screen is displayed briefly, before disappearing. Some Chinese text is then displayed in the upper-left corner of the screen. However, a ghost version of the woman image will appear along with a scream sound effect. When the screamer ends, it will immediately return to the woman picture. The screamer picture will appear suddenly.
A similar version of this application exists, called hikaru.exe. Both programs seem to do the same things, but they have a different screamer picture.