A Trojan horse is a common type of rogue software. The term ‘trojan horse’ is used to describe something that appears to be a gift, but that actually is a trap. In the computer security, the term has materialized into ‘a program that appears to be cool, but that erases all files’.
Trojan horses have been around since the first computers. One of the simplest and oldest types of Trojan horses is a password-stealing program.
These are especially common on shared computers used by many different people such as those in a school computer laboratory.
A trojan horse is a type of computer program that programs an ostensibly useful function but contains a hidden function that compromises the host system’s security. In contrast to viruses and worms, Trojans do not duplicate.
An author of a Trojan horse program might first create or gain access to the source code of a useful program that is attractive to other users, and then add code so that the program performs some harmful function in addition to its useful function.
Just like the ancient Greek ruse from which is derives its name, Trojan horse programs rely on trickery. Trojan horses usually run only once, but that is enough to wipe out files, steal passwords or cause other types of damage.
Once the user loads it on the machine, the Trojan horse will then either deliver a second program, such as a virus or worm, or simply take some malicious action itself.
Since Trojan horses are usually installed by users themselves, the security countermeasure for this attack is to prevent downloads and installation by end users.
What is Trojan horse in computing?