Moodle is a powerful tool, but it is not able to prevent all methods of cheating. If you would like to learn more about security and how to prevent students from cheating, check out the following documentation on Moodle's own website: Moodle docs
You can also "Lan School" for your examination. For more information click here.
The other option that can be explored is using the " Safe Exam Browser". For more information Click here.