Mutations are always a loss of information and damage to the genome. This loss can be a good thing but usually a bad thing.
All known mutations result in a loss of information. There is no empirical observations that show a mutation that results in an increase of information.
A classic example is the sickle anemia. This is a point mutation where a T and A on the DNA switch places. This results in a damaged red blood cell. In malarial zones this is a good thing. The damaged red blood cell opens up allow the immune system to combat the malaria protozoa. However in non malarial zones this is a bad thing as the sickle cell episodes can be life threatening.
The blind fish of death valley are another example. In the total darkness of the underground rivers and lakes, the mutation(s) that resulted in the loss of eye tissues is a good thing. The loss of the eye protects the fish from serious injuries and the loss of sight is no loss in the total darkness. This loss of information helps the blind fish.
Bacterial resistance to antibiotics is also due to a loss of information. "
For example, a mutation resulting in antibacterial resistance is very beneficial to the bacteria, and so it is "good" in the sense that it allows the species to survive when exposed to anti-bacterial substances.
However, some mutation decrease the chance of an organism being able to survive in its environment. For example, a mutation resulting in a butterfly changing colour may make it more visible to predators, and so the organism is less likely to survive and the mutation is "bad".