What is a Trojan?

The trojan horse is an ancient trick to bypass defenses

According to the legend, the ancient Greeks couldn’t capture the great city of Troy even after years of war. To achieve their goal, they came up with a plan: masking a wooden horse big enough for 40 men to hide in as a gift to the Trojans. Once the Trojans dragged the horse inside the city walls, the 40 men inside let in a greater force and the city was captured. A Trojan computer virus works just like the famous Trojan horse of Greek legends: disguising a virus as something else to get through your defenses undetected.

A Trojan is a way for criminals to get into your device

It’s not that easy to get past cyber security measures. Cyber criminals are well aware that a file called virus.exe won’t fool anyone. There­fore, it has to be disguised. Once the virus is in your device, it can steal your personal data, such as pass­words, or banking information. It can also spy on you, send spam messages and encrypt your files for ransom. Once a Trojan infects your device, it can down­load other viruses with­out you knowing or use the infected computer to carry out attacks as a part of a larger net­work.

A Trojan horse virus is masked to attract you

A computer Trojan can be disguised as practically any­thing that gets your attention. An email attachment claiming to be an invoice, or vital con­temporary information? Sure. A viral cat video? You bet. An interesting app? Yes, and so much more. Trojans are often injected into a program or a file you want to down­load. Unfortunately, these tricks can be really difficult to spot. They are, after all, meant to fool you.

There are many ways for Trojans to infect the devices of unsuspecting users. Common ways of infecting a victim’s computer with a Trojan horse virus include phishing messages and so-calleddrive-by down­loads where the Trojan is sneaked into the device. Phishing is a social engineering method where malicious programs are disguised as links and attachments in an email, for instance.

What are the different types of Trojans?

As if defending against Trojan horse attacks was not difficult enough, there are different kinds of Trojans to look out for. Trojans can be developed based on cyber criminals’ needs and some of the more sophisticated trojans can fulfill multiple functions. Trojans, and malware in general, can also be sold by cyber criminals to other criminals based on their needs. Here are a few common types of Trojan malware:

Back­door Trojan

As their name suggests, back­door Trojans create a kind of back­door: a gate­way used to enter into your device. When a back­door Trojan has established a path into your computer or mobile device, it can use this back­door to enter. The back­door can be used to steal your information or infect the device with malware such as spy­ware and other trojans.

Banking Trojan

Banking Trojans are looking to steal your banking information, such as bank account login details. For example, the victim of a banking Trojan may receive a malicious link in a phishing attack. After clicking a link, the user is taken to a page that looks like the login page of their bank. Instead of logging in to their online bank, the victim is unknowingly giving their bank account details to cyber criminals. Banking Trojans can be used to steal your credit card information as well.

DDoS Trojan

DDoS is short for the term Distributed Denial of Service. In practice, this means that a server is bombarded with requests to increase the server’s traffic over its limit. The word distributed here refers to multiple different sources that are simultaneously attacking the server. In case only a single source is responsible for all traffic, the term DoS is used. A trojan horse virus can connect a user’s device into a larger net­work of devices called a botnet and use the device to carry out DDoS attacks.

Down­loader Trojan

Once a down­loader Trojan has infected a device, it can down­load other harmful malware on the device. Down­loader Trojans are similar to Trojan droppers. The difference between down­loader Trojans and droppers is that droppers already contain the harmful program whereas a down­loader Trojan is used to down­load the program from an external source. The viruses or other Trojans delivered in a dropper are called the dropper’s payload.

3 tips for avoiding Trojans

The Greeks would have never captured Troy, had the Trojans not taken the horse in. Similarly, Trojan viruses cannot infect your device unless you let them in. There­fore, being safe requires your action. Here are a few things you can do to protect your­self against Trojan malware.

1. Use anti­virus soft­ware

Anti­virus is like the walls of Troy. It blocks malware from infecting your device and acts as a Trojan remover. You can also scan files you may want to down­load for anything suspicious and check in case an interesting file is in fact a Trojan horse.

2. Avoid opening links and attachments

Email attachments and links are one of the most common distribution methods for Trojans. Only down­load and open files and apps you trust from reliable sources. This applies both to computers and mobile devices, as your iOS and Android phone is susceptible to Trojans as well.

3. Don’t fall for phishing scams

Phishing and smishing scams can take you to down­load pages or infect your device with malware. Don’t fall for easy traps and be suspicious of unsolicited emails and messages with links or attachments.