A Trojan (Trojan horse) is malware disguised as a legitimate or useful program, which the victim installs voluntarily and which then performs hidden malicious actions.
How a Trojan works
The name comes from the wooden horse of Greek legend. Unlike viruses and worms, a Trojan does not copy itself – it relies on deception. It arrives as a cracked game, a fake update, a “document” in an email attachment, a browser extension or an app in an unofficial store. After launch it may show the promised function while working in the background.
Trojans are classified by what they do:
- downloaders and droppers install further malware;
- remote access trojans give full control over the device;
- banking trojans steal online banking logins and manipulate transfers;
- infostealers collect passwords, cookies and crypto wallets;
- backdoors open a hidden entry point for the attacker.
Why Trojans matter for security
Trojans are the most widespread type of malware and often the first stage of bigger attacks. Emotet, which started as a banking trojan in 2014, became a delivery service for other gangs until an international police operation dismantled its infrastructure in 2021. On Android, trojans hidden in apps abuse accessibility services to read screens and approve transactions.
How to protect yourself
- Download software only from official websites and app stores; avoid cracks and keygens.
- Do not enable macros or run files from unexpected emails.
- Check app permissions, especially accessibility and device administrator rights on Android.
- Keep security software and the operating system updated.
