A bump key is a specially cut key that allows it to be used in a pin-tumbler lock. Now if you are wondering how likely it is that your home has pin-tumbler locks, they are among the most common type of lock in the world so you will, no doubt, see the need for concern. Bump keys are also quite easy to acquire, you just have to know the manufacturer of the lock you want it for. Using this type of key does not take very much time to master and very little skill is needed which would appeal to a would-be intruder.
What can you do to minimize the likelihood that an intruder would use a bump key on your door? It is possible to obtain bump proof locks, but these can be difficult to find and expensive. You may find it easier to find a bump-resistant type of lock as these a more common.
You may also want to consider some different form of security system which would raise an alarm if someone tried to break into your home.