One sub-topic under this is Infections. They make computers sick. One such animal (no punn) is the Trojan Horse. This creature hides within an executable programs and can eat away your data. Under the Trojan Category you may also find what is called a Logic Bomb. In order for this to activate a certain set of criteria must be met. Ex. If the result is B then eat away the data! Everytime the program is run and the B result happens you can say bye bye to your data.
Also common is the term VIRUS. They are also considered parasites. They can reproduce themselves. These can be particular about what they infect. Some will on effect .com files (Friday the 13th .com). Even more specific they happen on at certain times. as with the Friday the 13th .com file will happen only then. Similar is the deadly Michelangelo. When happens on March 6, birthday of the artist. When it strikes it will reformat your hard drive!
I guess with any sickness the main concern is prevention... Certain data can be blocked from passing through on systems via what is called a Firewall. These can only allow authorized personnell in certain areas. It is very important that data be backed up. (Disk or preferable Tape)
There is the story of a person, who brought six thousand computers connected to the Internet to a halt. This was accomplished through a WORM (spreads from system to system). As a result prevention groups were formed to combat this breach of security, such as the Forum of Incident Response and Security Teams (FIRST).
One person asked me about other means of protection. It is good if on your PC with your Autoexec.bat file, you load a virus protection program each time your system boots up. If believe a version of Central Point comes with Dos 6. Additionally you may be very concerned about programs you download (take from a host system and bring to yours). I have had one person say that what can be done is that when you are prompted by the Host System as to where the file is to be downloaded, you request a download to your A drive then scan that drive as oppossed to downloading directly to your C drive.
All of this said, can we ever be certain that the Data is Secure? As always your comments and suggestions are welcome. Hoping your Cybertravels are SAFE ones....