What is a trojan?
A trojan horse could be either:
a) Unauthorized instructions contained within a legitimate program. These
instrcutions perform functions unknown to (and probably unwanted by) the user.
b) A legitimate program that has been altered by the placement of anauthorized
instructions within it. These instructions perform functions unknown to (and
probably unwanted by) the user.
c) Any program that appears to perform a desirable and necessary function but
that (because of unauthorized instructions within it) performs functions
unknown to (and probably unwanted by) the user.
Under a restricted environment (a restricted Unix shell or a restricted
Windows computer), malicious trojans can't do much, since they are restricted
in their actions. But on a home PC, trojans can be lethal and quite
Why the name 'trojan horse'?
In the 12th century B.C., Greece declared war on the city of Troy. The dispute
erupted when the prince of Troy abducted the queen of Sparta and declared that
he wanted to make her his wife, which made the Greeks and especially the queen
of Sparta quite furious.
The Greeks gave chase and engaged Troy in a 10-year war, but unfortunately
for them, all of their efforts went down the drain. Troy was simply too well
In a last effort, the Greek army pretended to be retreating, leaving behind a
hude wooden horse. The people of Troy saw the horse, and, thinking it was some
kind of a present from the Greeks, pulled the horse into their city, without
knowing that the finest soldiers of Greece were sitting inside it, since the
horse was hollow.
Under the cover of night, the soldiers snuck out and opened the gates of the
city, and later, together with the rest of the army, killed the entire army of
This is why...