There is one very nice article on copyright protection at the AIGA center for practice management. It explains how designers could deal with copyright infringements and protect their work.
There are a couple of ways to protect your intellectual property—patents, copyrights, trademarks, trade dresses. If you intend to use any of them, contact an attorney.
Although intellectual property instruments are there to help us protect our work, they were not meant to make people fight against each other, when they should have innovated more. Generally, they are not of a long-term interest for the society.