Experiment all you want, but don't try to override existing security. Respect other users and their data. For example, you should not browse through other users' directories unless they have given you specific permission to do so. To ensure the privacy of your own files, be sure to set the permission flags accordingly. Don't share your account, and never tell someone else your password.
Accounts are for the exclusive use of the account holder.
Permitting more than one user on each account is an unacceptable security risk for the whole system. Second, anyone who uses your account will introduce themselves as you to potentially thousands of people across the world, via the Internet. Please do not make excessive or inappropriate demands on our resources. The SCCS is likely to be fairly busy, so if you have UNIX access elsewhere on campus, we encourage you to make use of it instead for CPU-intensive tasks, if possible. We ask that you keep the size of your home directories as small as possible, since disk resources are tight also.