A ‘Trojan Horse’ or Trojan is named after the Greek myth. It is a program that has been installed on you computer without your knowledge.
It usually carries a payload of malicious code, that could for example allow surreptitious external connections to your computer. Some trojans leave ports open so as anyone can connect to your computer, others restrict access to certain users.
Once access is gained the intruder can do anything from monitor your behaviour to taking complete control.
There are many ways Trojans can infect your computer. A person with physical access to your machine can place it there, but you can also accidentally install it yourself by opening an infected email attachment.
FAQ Category: Glossary of terms used