Ethics is the field of study that is concerned with questions of value, that is, judgments about what human behaviour is "good" or "bad". Ethical judgments are no different in the area of computing from those in any other area. Computers raise problems of privacy, ownership, theft, and power, to name but a few.
Computer ethics can be grounded in one of four basic world-views: Idealism, Realism, Pragmatism, or Existentialism. Idealists believe that reality is basically ideas and that ethics therefore involves conforming to ideals. Realists believe that reality is basically nature and that ethics therefore involves acting according to what is natural. Pragmatists believe that reality is not fixed but is in process and that ethics therefore is practical (that is, concerned with what will produce socially-desired results). Existentialists believe reality is self-defined and that ethics therefore is individual (that is, concerned only with one's own conscience). Idealism and Realism can be considered ABSOLUTIST worldviews because they are based on something fixed (that is, ideas or nature, respectively). Pragmatism and Existentialism can be considered RELATIVIST worldviews because they are based or something relational (that is, society or the individual, respectively).
Thus ethical judgments will vary, depending on the judge's world-view. Some examples:
First consider theft. Suppose a university's computer is used for sending an e-mail message to a friend or for conducting a full-blown private business (billing, payroll, inventory, etc.). The absolutist would say that both activities are unethical (while recognising a difference in the amount of wrong being done). A relativist might say that the latter activities were wrong because they tied up too much memory and slowed down the machine, but the e-mail message wasn't wrong because it had no significant effect on operations.
Next consider privacy. An instructor uses her account to acquire the cumulative grade point average of a student who is in a class which she instructs. She obtained the password for this restricted information from someone in the Records Office who erroneously thought that she was the student's advisor. The absolutist would probably say that the instructor acted wrongly, since the only person who is entitled to this information is the student and his or her advisor. The relativist would probably ask why the instructor wanted the information. If she replied that she wanted it to be sure that her grading of the student was consistent with the student's overall academic performance record, the relativist might agree that such use was acceptable.
Finally, consider power. At a particular university, if a professor wants a computer account, all she or he need do is request one but a student must obtain faculty sponsorship in order to receive an account. An absolutist (because of a proclivity for hierarchical thinking) might not have a problem with this divergence in procedure. A relativist, on the other hand, might question what makes the two situations essentially different (e.g. are faculty assumed to have more need for computers than students? Are students more likely to cause problems than faculty? Is this a hold-over from the days of "in loco parentis"?).