One of the ways to protect information is by limiting what people can do with your information and resources. Like a private letter, you may allow a friend to read it, but not edit it. Your friend may make a mistake. You might let a teacher edit it because she will correct it.
Newbie: Like the letter example mentioned, there are limits to what others should be able to do to your work. To apply it to the cyber realm, you would not want to allow others to change important settings or create users with too many permissions. They could make an account with superuser or administrator rights that could be used to bring down your whole system! Always double check who has what permissions.