Code Of Conduct
As a computer scientist, or someone taking a computer science class, you are expected to perform your work at all times in an ethical manner. This means that in addition to doing your own work and giving appropriate credit when the work of others is used, you are required to protect your work.
A student that protects their work will not allow another student access to that work whether it be allowing it to be copied, or treating its security in such a way as to give unintentional access, such as "accidental" loss. It is the policy of the department that when duplicate (essentially the same) work is turned in by two or more students, without acknowledgement of allowed cooperation, all involved students will be considered in violation of this department policy. Under such circumstances, each student will receive minus the points possible for the work.
Thus, for a 15 point assignment, all would receive -15 points. If the infraction is deemed more egregious, then further action may be taken.