A Trojan, also known as a Trojan horse, is a type of malicious software or malware that disguises itself as legitimate software. The term derives from the Ancient Greek story of the wooden horse that was used to infiltrate the fortified city of Troy during the Trojan War.

Trojans can be employed by cyber-thieves and hackers trying to gain access to users’ systems. Once installed on a user’s computer, a Trojan can perform actions ranging from stealing sensitive data to allowing the attacker to gain control over the computer.

Unlike computer viruses and worms, Trojans are not able to self-replicate, which means they cannot spread by making copies of themselves. Instead, Trojans rely on unsuspecting users to install them, typically through social engineering tactics such as phishing emails or malicious websites that appear to be legitimate.

There are several types of Trojans, each designed to perform specific functions:

  1. Backdoor Trojans allow attackers to control the victim’s computer remotely, often for the purpose of creating a network of infected computers known as a botnet.
  2. Downloader Trojans are used to download and install new versions of malicious programs onto the victim’s computer.
  3. Info-stealing Trojans can harvest data from a system, including login credentials and personal information, which can then be used for things like identity theft.
  4. Ransomware Trojans encrypt files on the victim’s computer and then demand a ransom to decrypt them.
  5. DDoS Trojans can perform distributed denial-of-service (DDoS) attacks against a targeted web address.

The best defense against Trojans is a multi-pronged approach that includes maintaining up-to-date antivirus software, practicing safe browsing habits, regularly updating and patching software, and not opening suspicious emails or attachments.