A trojan horse, or trojan, is a form of malware that disguises itself as a harmless file or application to mislead users of its true objective. The trojan will be released on the user s device with a click or download of the seemingly innocent program. This allows the malicious code to perform whatever task the attacker intended. Unlike viruses and worms, trojans do not reproduce or self-replicate.
The name for this malware comes from the Greek legend of the Trojan War, in which the Greeks gift the Trojans a giant, wooden horse. After the horse was accepted into Troy s city walls, Greek soldiers emerged from their hiding place within the horse and opened the city gates, which led to the capture of the city.
Types of trojan horses
- Backdoor allows attackers full access and control of the computer it infects.
- Banker steals banking account information.
- Data Sending sends sensitive data from a device to the attacker by searching the device or keylogging.
- Distributed denial of service (DDoS) uses multiple devices infected by trojans to overwhelm and flood a network which leads to a denial of service.
- Destructive trojans destroy and delete files.
- Downloader trojans download and install malicious software and programs.
- Game-thief steals online gamer s account information.
- Mailfinder steals email addresses from your mail history.
- Proxy trojans use the infected computer as a proxy or zombie to conduct illegal activities undetected.
- Ransom trojans steal data or damage your computer, and the attacker requires a ransom to release your data or repair the damage.
- Rootkit hides the malware on your device to extend the time that the program can run.
- SMS infects a mobile device and can send and intercept text messages.
How to avoid trojan horses
As you can see from the list above, trojans can steal sensitive information and cause a lot of serious damage. Fortunately, there are a few steps you can take to avoid this malware:
- Don t open an attachment or run a program found in an email from an unknown sender.
- Only download software from sources you fully trust.
- Avoid clicking on pop-ups that promise free software.
- Keep your computer and its software up to date.
- Install and regularly run an antivirus program on your computer.
Signs of a trojan horse
- Desktop changes
- Increase of spam or pop-ups
- Poor device performance
- Unfamiliar downloads, add-ons, or applications
- Changes to display color, clarity, or orientation
- Strange device behavior