A Trojan Horse, often called a “Trojan,” is a type of malicious software (malware) that disguises itself as a legitimate or harmless program or file to trick users into downloading and running it on their computers.
Once executed, the Trojan can carry out various harmful activities, such as stealing sensitive information, damaging files, or granting unauthorized access to the infected computer.
In other words, the Trojan Horse in Computer is like a wolf in sheep’s clothing – it pretends to be something harmless but is designed to cause harm once inside a system.
History of The Trojan Horse
In this tale, the Greeks wanted to enter the city of Troy, but the city’s walls were too strong to break through. So, they came up with a clever plan. They built a huge, hollow wooden horse and left it outside the city gates as a supposed gift.
The Trojans, believing the Greeks had given up and left, brought the wooden horse inside the city as a symbol of victory. That night, the Greek soldiers hidden inside the horse emerged and opened the gates of Troy from within, allowing the Greek army to enter and conquer the city.
Now, when it comes to computer viruses, people named one type of malware after this ancient story. It’s called a “Trojan Horse” because, like the wooden horse, it pretends to be something harmless, like an innocent-looking email attachment or a free download, but it actually carries harmful code or actions.
Just like the Greeks used the wooden horse to sneak into Troy, cybercriminals use Trojan Horse malware to sneak into your computer and do bad things.
How Do Trojans Work?
For a Trojan horse to harm a computer, the user must first get the harmful part of the program. The Trojan can’t do anything on its own. The user needs to put in the executable file (.exe file) and set up the program, and only then can the attack happen on the computer’s system.
Social engineering tactics are often used to fool people into downloading harmful apps. They may hide the trap in banner ads, website links, or pop-up ads.
The most common way to spread Trojan horses is through emails that seem harmless. These emails often come with attachments that are actually traps. The creators of these Trojan horses often use spam techniques to send these emails to hundreds or even thousands of people.
Once the email is opened and the attachment is downloaded, the Trojan server gets installed and starts running automatically whenever the computer is turned on.
An infected computer can also pass on the Trojan horse to other computers, which can lead to the creation of a botnet.
This happens by taking over a regular computer and making it act like a zombie. The person using the infected computer often doesn’t even know it’s being controlled by someone else. Hackers then use these zombie computers to keep spreading more malware and build a network of these controlled machines.
It’s not just people using laptops and desktop computers who need to be cautious. Trojan horses can also target mobile devices like smartphones and tablets with mobile malware. When this happens, attackers can take control of these Wi-Fi-connected devices and use them to carry out cybercrimes, like redirecting internet traffic.
Types of Trojan
The following are some of the most popular Trojan types:
1. Backdoor Trojan: These Trojans create a hidden “backdoor” into your computer, allowing cybercriminals to gain unauthorized access and control over your system. Once inside, they can steal data, install other malware, or use your computer for malicious purposes.
2. Downloader Trojan: Downloaders are designed to secretly fetch and install additional malware on your computer. They act as a gateway for other malicious programs, making your system vulnerable to various threats.
3. Keylogger Trojan: Keyloggers record every keystroke you make, potentially capturing sensitive information like passwords, credit card details, and personal messages. Cybercriminals can then use this data for identity theft and fraud.
4. Banking Trojan: These Trojans specifically target financial information, often when you access online banking or payment systems. They aim to steal login credentials and sensitive financial data, enabling attackers to siphon funds or commit fraudulent transactions.
5. Ransomware Trojan: Ransomware Trojans encrypt your files, making them inaccessible. Attackers then demand a ransom payment in exchange for the decryption key, often with the threat of permanent data loss if you don’t comply.
6. Remote Access Trojan (RAT): RATs allow hackers to gain full control of your computer from a remote location. They can access your files, turn on your webcam, record your screen, and perform various activities without your knowledge or consent.
7. Rootkit Trojan: Rootkit Trojans are deeply embedded within your system, making them difficult to detect and remove. They often manipulate system functions, hide from antivirus software, and provide attackers with persistent access and control over your computer.
8. Distributed Denial of Service (DDoS) Trojan: These Trojans turn your computer into a part of a botnet, a network of compromised devices. Cybercriminals use these botnets to flood websites or online services with an overwhelming amount of traffic, causing them to become inaccessible. This is a common tactic in cyberattacks against websites and online platforms.
Examples of Trojan Horses
Throughout the years, antimalware companies, security experts, and even everyday people have uncovered various Trojan horses. Some of the most well-known discoveries include:
- Zeus: First detected in 2007, Zeus remains one of the most dangerous banking Trojans globally. It allows hackers to create their own Trojan horses and use techniques like form grabbing, keylogging, and polymorphic variants that capture victim credentials through drive-by downloads.
- Magic Lantern: Developed by the FBI around the year 2000, Magic Lantern is a government Trojan that logs keystrokes and aids in criminal surveillance.
- Tiny Banker (Tinba): Researchers identified this Trojan in 2012 after it was used by attackers to steal sensitive financial information from major U.S. banks.
- Bitfrost: This remote access Trojan (RAT) infected Windows clients by manipulating and creating system components.
- FakeAV Trojan: This Trojan posed as an official alert in the Windows system tray, tricking users into downloading more malware when trying to fix a non-existent computer problem.
- Stuxnet: Discovered in 2010, Stuxnet is a complex worm that targeted supervisory control and data acquisition (SCADA) systems. It was notably used to disrupt Iran’s nuclear program.
- Conficker: First detected in 2008, Conficker is a worm that spreads through network vulnerabilities, creating a massive botnet and causing significant damage to computer systems.
- Emotet: Known as one of the most dangerous and prolific banking Trojans, Emotet spread via malicious email attachments and was involved in various cybercrimes, including distributing other malware.
How To Recognize and Detect a Trojan
When you suspect that a Trojan may have compromised your device, you should be on the lookout for common signs of malicious software, including:
- Poor device performance: Is your computer or mobile device running noticeably slower or experiencing more frequent crashes than usual?
- Strange device behavior: Are there programs running on your device that you didn’t start, or are you noticing unexplained processes being executed on your device?
- Pop-up and spam interruptions: Are you seeing an increase in the number of annoying interruptions from browser pop-ups or email spam?
These signs can indicate a potential Trojan infection and should prompt you to investigate further or seek assistance from security professionals.
How To Remove a Trojan Horse
If you discover a Trojan horse on your computer, here’s how to get rid of it:
- Disconnect from the Internet: First, disconnect from the Internet to stop the Trojan from doing more harm.
- Use antivirus or antimalware software: Run your antivirus or antimalware program to find and remove the malicious files. If you’re unsure which files are infected, look for errors or warnings, like DLL errors, which can give you clues.
- Disable System Restore: Turn off the System Restore function to prevent the malicious files from coming back.
- Restart in Safe Mode: Restart your computer and, during the restart, press the F8 key to start in Safe Mode. This helps you remove the infected programs.
- Remove infected programs: In Safe Mode, go to the Control Panel and open “Add or Remove Programs.” Delete the programs that are causing trouble. Make sure to delete all related files to be thorough.
- Restart normally: After doing all this, restart your computer as usual. This should complete the removal of the Trojan horse.
Is Trojan Horse a VIRUS or MALWARE?
While some people may call it a “Trojan horse virus,” this term is technically incorrect. Unlike a computer virus, a Trojan horse cannot copy itself or spread on its own. It relies on the user’s help to operate. Attackers have to use social engineering tricks to deceive the user into running the Trojan.
Because there are numerous types of Trojan horses, the term can serve as a broad category for delivering malware. Depending on what the attacker wants and how the Trojan is built, it can operate in various ways.
Sometimes, it acts independently as malware, while in other cases, it serves as a tool for different activities like delivering harmful payloads, exposing the system to attacks, or allowing communication with the attacker.