Every spell can be dangerous at one point. You have something called consequences, everything you do including with magic has consequences. There is no way to measure how much something might backfire and there is no way to completely measure how much effect something might have on the rest of the world. Magic is manipulation of natural energy, to use it is to affect reality outside the manner it was naturally carrying on.
For instance if you cast a healing spell, that is still black magic by this definition because you have the personal satisfaction of helping someone even if by some chance they don't want to be helped. If you cast a healing spell it may still be considered white magic by this definition even if the person them self doesn't want to be healed, but perhaps someone else does and they become satisfied.
You never know who you are really truly pleasing except for yourself.
The point is, that as long as you properly protect yourself and know what you're doing - you're fully safe.
In my experience when i first started casting spells i dont protection spells but its diffrent for everyone. Too be honest aswell my first attept to cast a protection spell well lets say it drained all of my energy and it did not work in the end, so not all of the easier ones are safe, like i said they "drian" your energy.