These are typically charge traps and add a few ADU counts to the pixel values of a column. They are caused by small defects in the CCD either during manufacture or by cosmic ray strikes during the lifetime of the camera. The Kodak sensors are more prone to these than the Sony sensors but neither type is completely immune. They can be fixed during processing by using dark frames or dithering and sigma combine during stacking.
Please note that these are not the same as a column defect. A column defect is a column with pixel values that are always saturated i.e. 65000 ADU counts. Unfortunately these can not be corrected by dark frames. If your camera develops a column defect please send an uncalibrated dark frame to our support team here.