In this era of computer "viruses" and international spying by "hackers" who are thousands of miles away, it is clear that computer security is a topic of concern in the field of Computer Ethics. The problem is not so much the physical security of the hardware (protecting it from theft, fire, flood, etc.), but rather "logical security", which Spafford, Heaphy and Ferbrache [Spafford, et al, 1989] divide into five aspects:
Privacy and confidentiality
Integrity -- assuring that data and programs are not modified without proper authority
Unimpaired service
Consistency -- ensuring that the data and behavior we see today will be the same tomorrow
Controlling access to resources
Malicious kinds of software, or "programmed threats", provide a significant challenge to computer security. These include "viruses", which cannot run on their own, but rather are inserted into other computer programs; "worms" which can move from machine to machine across networks, and may have parts of themselves running on different machines; "Trojan horses" which appear to be one sort of program, but actually are doing damage behind the scenes; "logic bombs" which check for particular conditions and then execute when those conditions arise; and "bacteria" or "rabbits" which multiply rapidly and fill up the computer's memory.
Computer crimes, such as embezzlement or planting of logic bombs, are normally committed by trusted personnel who have permission to use the computer system. Computer security, therefore, must also be concerned with the actions of trusted computer users.
Another major risk to computer security is the so-called "hacker" who breaks into someone's computer system without permission. Some hackers intentionally steal data or commit vandalism, while others merely "explore" the system to see how it works and what files it contains. These "explorers" often claim to be benevolent defenders of freedom and fighters against rip-offs by major corporations or spying by government agents. These self-appointed vigilantes of cyberspace say they do no harm, and claim to be helpful to society by exposing security risks. However every act of hacking is harmful, because any known successful penetration of a computer system requires the owner to thoroughly check for damaged or lost data and programs. Even if the hacker did indeed make no changes, the computer's owner must run through a costly and time-consuming investigation of the compromised system [Spafford, 1992].

