changing a pointer rather than erasing memory cells

Computer Science An Overview _J. Glenn Brookshear _11th Edition

In a data structure based on a pointer system, the deletion of an item usually

consists of changing a pointer rather than erasing memory cells. Thus when

an entry in a linked list is deleted, the deleted entry actually remains in

memory until its memory space is required by other data. What ethical and

security issues result from this persistence of deleted data?