A type of 'malware' software.
A trojan seems to do an useful task and so the user will use it. But in the background, the trojan is also carrying out its real purpose which is hidden and unknown to the user.
For example, you download a free game, it's great! You keep on using it. But meanwhile the trojan may also install a permanent keylogger that now tracks every keystroke you make and sends it off over the internet to whomever created the trojan.
Beware of free gifts! as the Greeks found out in the story of the Trojan Horse.
Challenge see if you can find out one extra fact on this topic that we haven't already told you
Click on this link: Trojan