Possibly calcuim deposit
You could try and wipe the film off with some vinegar and a cloth. If this works then simply check that there is rinse aid and salt in the machine and that the dishwasher is set up according to the hardness of the water in your area. If you are using 'all in one' tablets instead then you can try putting some salt in to enhance the cleaning results from the tablets. Also check the cap on the salt compartment is shut tightly.
If the vinegar does not remove these marks, then the marks have been left by hard water deposits that are found in your water supply. Simply add salt to the dishwasher in the container at the bottom of the tub. In hard water areas this may need to be set to the maximum dosage. Your local water supplier can advise you if the water where you live is hard or soft.
example of the cloudy marks left by hard water