Trojans

A Trojan is malware that disguises itself as legitimate or desirable software, so you install it voluntarily. It might pretend to be a browser update, a free photo editor, or a security tool offering to clean up your computer. The installer looks normal or does something useful, which is why you run it instead of deleting it.

Once a Trojan is running, it can cause harm in three main ways:

• Damage the system - deleting, corrupting or changing files and settings so the computer stops working properly.
• Take control of the computer - changing what the computer does or installing other software without your knowledge.
• Give the attacker access - letting someone outside read your files, watch what you do or use your computer for their own purposes.

A Trojan does not self-replicate. It cannot copy itself into other files or send itself to another computer on its own; it relies on tricking a user into running it. For example, a student clicks a pop-up saying their browser is out of date and installs the 'update'. The browser still works afterwards, so nothing seems wrong. While it runs, it could quietly let an attacker connect to the computer or delete saved files. If the student never ran the fake update, that Trojan could not act.