CopyScape is an Excellent Plugin & Service

If you concerned about duplicate content and Google rankings then you need some type of plagiarism checking software. I found CopyScape to be highly recommended, inexpensive, easy to use and multiple capabilities. I had a little trouble with the API, but I realized I was capitalizing the first letter on my user name. (Don’t capitalize the first letter of your user name.) Once I figured that out it works great! The WordPress detail page states CopyScape has not been tested with the latest version of WordPress(3.9.1), but I’m not having any problems.