There is evil in the world, everywhere. A biblical Christian would even say that there is a cabal of unseen conspirators promoting it. Where did it come from, and how did it manage to sprout like weeds under the eye of an omniscient and omnipotent God? To answer, "de Debil,"a la Mama Boucher, is too facile and adds no true value to understanding the ultimate question. The Devil is evil, it's in his name. He is the father of much that is evil in the world today, but where did his evil come from?
The Bible tells us that mankind is inherently evil. I agree and would attribute their evil to the same source as the Devil's. It wasn't God for he is inherently good-- at least it wasn't him, directly. God is the ultimate free moral agent. He is sentient with powers of will and choice, and he made mankind and angels with similar powers and turned them loose in creation with freedom. Therein, is the seed of evil.
How can those abilities which so distinguish us from the plethora of slime and the menagerie of the mobile be responsible for evil? I'll have to define evil before proceeding: evil is that which is not good, and by extension, that which is out of harmony with God. Evil is the un-God. When choice and will were expressed independently of, and in opposition to God, evil was born. Evil was the the risk intrinsic in freedom.
All that is was made as the home of God's crowning creation-- mankind. When man embraced evil and shattered the crystal of the pristine environment, they alienated both the creation and the creature from God and what is good. As a result, sin and death, evil and it's fruit, have spattered everything in the universe and infiltrated all that is alive and inanimate. Man, beast and the environment we live in has all been tainted by evil. Creation may still bear the fingerprints of God, but its smudges betray, all too clearly, that it was also touched by a "fallen angel."