Viper Plagiarism Scanner 

Find out if a document is truly original or if it has been plagiarized by comparing it against other texts available on the Internet. The tool scans a huge array of online sources as well as your own document library, then shows whether the document you're checking is similar to others or not.

Viper Plagiarism Scanner is a piece of downloadable software that is used to detect plagiarism in electronic documents. It scans the web, the user's past document library (optionally), all past submissions to the program, and millions of electronic resources such as books and journals.