The W32/Cisum.A worm copies itself under the name ProjectX.exe to the root directory of the shared drives on the computer. It then displays a window containing the text "YOU ARE AN IDIOT!", while playing an MP3 sound file repeating the same phrase. The virus alters a number of registry entries to trigger off a service called "ProjectX.exe" which starts off the audio file and message box.
The virus also disables anti-virus software and other security applications. While not the first virus to play a sound (Netsky.C was the first), it is certainly one of the most insulting.