Mate, you could copy 100% from sources such as the internet and still not get caught. The only way you could get caught for plagiarism is if you copy a class mate in which case the exam board will run the course work through a plagiarism checker through a system most commonly used in universities. You are not allowed to pass any of the work or ideas from other sources with or without the owners their consent so any work/idea from the internet could be extremely reckless if your friend also have the same or similar ideas.