Many people believe that since God created all things, He must also have created evil. Apologist Greg Koukl offers insight into this commonly asked question. This analogy originated with St. Augustine and was further developed by Thomas Aquinas. Consider the issues of light or temperature. Light is a thing, made up of particles or waves.
Temperature works the same way.
Cold is not a thing, but the absence of heat, which is a created thing. Take away the element of physical motion which creates heat as we know it and you are left with cold. Cold is not created, neither is darkness. They are the absence of the created things. Evil, then, is not a created thing, but the absence of good.