Donn Parker's Categories of Hacker [1]:

benign
- the hacker whose intentions are purely educational
unsavory
- the intruder whose intentions are not necessarily malicious but whose very presence can be negative
malicious
- the intruder whose primary intention is to cause the system to crash or to wreck havoc in its operation

[1] Parker, Donn, and John F. Maxfield. 1985. "The Nature and Extent of Electronic Computer Intrusion", Workshop on Protection of Computer Systems and Software, National Science Foundation.
Lightly edited 96/04/30
J.A.N. Lee