Bob Atkins , Apr 28, 2012; 03:05 p.m.
They are "hot pixels". They are normal and not considered a "defect".
They can be removed by dark image subtraction or there are software packages that can be used to remove them. Alternatively you can clone them out or better still, stop looking for them at 100% magnification on your monitor. It's very unlikely you would ever notice them in a print.
They are caused by things like leakage current. They are defects in the sense that they are not supposed to do that, but all sensors have them. You don't get 20 million perfect pixels unless you are very, very lucky. All sensors have most of their more serious "problem pixels" mapped out by the camera maker so you never actually see them.