The Cobra Effect refers to an attempt at trying to solve a problem, only to make it worse.
The name comes from the British rule of India, in which the government was concerned with the high number of venom cobras in Delhi, to which they offered a bounty to the people there for every dead snake they bring in. However, this move resulted in people capturing and breeding snakes, so they could produce more snakes to get more money. Once the British found out about this, they scrapped the program, and the snake breeders released all the snaked back into the wild, which ironically increased the snake population.