Internet Plagiarism

It's know for everybody that Internet is the big source of information nowadays. The problem start when people like students use this information to complete their works without their personal work. I think that it's not right, because it decrease the educational level but it's very difficult for teachers to discovers if a student has copy or not. Certainly we can't do nothing to stop this because normally the information extracted for Internet is very useful for all the world. The solution more appropiate is be more concerned about students works.