Google. When given a written or a research assignment, many would simply google the keywords, download the related articles, copy and paste parts of the article, and voila the assignment is done. Interestingly enought, most of the copied articles can be found on Wikipedia.
[As a side point which is not really relevant to this posting, is "google" an accepted verb in the English language?]
Anyway, the copy-and-paste article would be handed to the lecturer for grading. The lecturer reads the assignment and notes that there are numerous grammatical and spelling errors in the introduction. Interestingly enough, the next sections and subsections contain perfect English. There is flair, there is substance, as if one is reading from a book written by the expert in the field, complete with references. Then comes the conclusion, which contains too many grammatical and spelling errors, similar to the introduction. When you get to the last part, which is the reference or bibliography, there is not a mention of the references that were used in the body of the article. What is there is just a list of a few books which are not even quoted in the write-up.
Of course, the lecturer would easily suspect that the article has been copied from the Internet. He/she can easily use softwares like Turnitin to verify his/her suspicion. One very simple way is just to pick at random a few sentences and use Google to search. Chances are you can easily get the exact parts that are copied, and more often than not (in the case of undergraduates), the copied articles are from Wikipedia.
The above is something that I believe most lecturers have come across with. I would always penalise those who simply copied and pasted from articles without citing or crediting the original author and publication. I also remind my students not to rely on Wikipedia as an authoritative source of reference. The nature of Wikipedia is such that anyone can contribute, hence the authoritativeness of the article can usually be disputed. The articles in Wikipedia can be used to identify references and points of discussion. In other words, they can be used as a starting point, but not as the only point of reference.
It is critical that undergraduates be aware of the "sin" of the copy-and-paste culture. Usually, research misconduct begins with this very simple act of copy-and-paste. This is the seed of plagiarism. Undergraduates must be made to understand that research integrity should be the priority. Cheating by copy-and-paste to get good grades is an act of a person with no integrity whatsoever.
If this copy-and-paste culture is allowed to be part of an undergraduate's culture, what is there to stop them from committing the same offence when they become postgraduates and members of the academia? In this day and age of the Internet, it is easy to plagiarise. Having said that, it is also equally easy to get caught.