It is sometimes unpleasant to discover a little annoying problem like a defective pixel on the sensor of a digital photo camera. It produces a small colored pixel (often black or white, sometimes of some other color). On a RAW file, it could be worse if it produces a colored streak.
It is most visible when shooting long exposures and the strategy used by most photo cameras is simply to shoot an additional black picture(without opening the shutter) just after the photo you wanted to find the hot pixels and remove/subtract them from the original photo. This is observable as a relatively long computation after a long exposure photo.
It takes time in the field and it uses up the camera electrical energy. So, here is a small tool that allow to transfer this operation toward the studio PC: PixelFixer.
The list of photo cameras this tool is compatible with contains a lot of cameras from Nikon, Canon, Pentax and Leica. No Sony I know of (they are left with the in-camera option that works well too).