Trojan Horses and Worms
A Trojan Horse
has a time delay. It waits for a date or event to trigger the code and
damage the computer. Trojan horses usually do not replicate themselves
or use mass-mailings. They often masquerade as useful programs, such as
weather alerts.
A Worm, on the other hand, copies itself using
email or another portal
mechanism. Both of these can appear in your
email as a joke or funny
screen saver.
Hoaxes
Another class
of viruses is the Hoax letter. The email claims that you have a virus
and you should search your computer and delete the specified file.
Usually, the so-called virus is a file that Windows needs. When you
throw away the file or program, you have disabled your operating system.
In affect, you shot yourself in the foot.