Trojan Horse Malware - Disguised Digital Threats

About 2 min read

A Trojan horse is a type of malware that disguises itself as legitimate software or files to trick users into installing it, then carries out malicious actions behind the scenes. Named after the Trojan horse of Greek mythology, it hides attack code inside a program that appears harmless. Trojan horses are known as one of the representative categories of detected malware.

Real-World Use Cases

For example, an employee might install a Trojan horse disguised as a productivity tool, allowing an attacker to gain unauthorized access to the internal network via a RAT. In such a case, the typical first response is to identify the infected endpoint from EDR logs, isolate it from the network, and scan all endpoints.

The Difference from Worms

A worm is easily confused with a Trojan horse. The biggest difference lies in whether they can self-replicate. A worm automatically spreads to other devices over the network, whereas a Trojan horse does not self-replicate and infects only when the user installs it themselves. In other words, a Trojan horse specializes in "deceiving," while a worm specializes in "spreading." Furthermore, while worms often cause damage by consuming network bandwidth, Trojan horses are used for more targeted attacks, such as installing a backdoor or stealing information.

Infection Routes and Types

Free software, pirated copies of games, email attachments, and fake software update notifications are the main infection routes. Banking Trojans steal online banking credentials, and RATs (Remote Access Trojans) give attackers complete remote control of the device. For example, a Trojan horse disguised as a free PDF conversion tool may extract all of the passwords saved in the browser after installation.

Defensive Measures

The basics are to download software only from trusted sources and not to open attachments in suspicious emails. To prepare for the event of an infection, setting a unique random password for each service means that even if one service's credentials are stolen, you can prevent the damage from spreading to other services.