There’s a lot of malware circulating in the digital world. One specific type is referred to as a Trojan horse — or more commonly as a Trojan. This form of malicious code is designed to harm or disrupt the recipient’s network. Often, this type of malware is also used to steal data or perform other malicious acts. Read on to learn how to spot a Trojan on your device and how to get rid of it. Also discover how Avira Free Security can help boost your cybersecurity.
What’s a Trojan?
A Trojan is a special type of malware. It aims to deceive users and trick them into running seemingly harmless computer programs. This is where this type of malicious code gets its name. Just like the Trojan horse from Greek mythology, which secretly smuggled soldiers into the city of Troy disguised as a gift, the Trojan horse also masks itself as something harmless or even useful. This entices users to allow the malware into their system.
Often, victims don’t notice the malicious code to begin with. However, the program can cause immense damage once executed. A Trojan can read passwords, record keystrokes, and install other malware on your computer. The latter can even take the entire computer hostage, locking you out of your own device.
By the way: Technically speaking, a Trojan is a special form of malware and not a computer virus. Unlike a virus, which can execute and replicate itself, a Trojan requires a user to execute it. Nevertheless, it’s also colloquially referred to as a Trojan virus.
How do Trojans work?
Trojans are often hidden in seemingly legitimate email attachments. Using various social-engineering techniques, cybercriminals manage to win the trust of their victims. It can appear to users that they’re receiving a message from someone they know.
They therefore consider the email and the attachment to be legitimate. However, if victims download and open the file, this executes the malware. Depending on the type of Trojan, it can spread to other files or even paralyze the entire device — be that a computer or smartphone.
What types of Trojan are there?
The number of Trojan types is always on the rise. They all have one thing in common, though: To take over a user’s device to snoop on them or steal data. They’re also used to install additional malware on the victim’s device, disguised as legitimate documents or programs. Here’s a breakdown of the common types of Trojans and the threats they pose:
- Backdoor Trojans: This cyberattack allows remote access to your system. Hackers can then control your device and infect it with additional malware. This type of Trojan also allows cybercriminals to steal your data and track what you get up to online. They can also turn your computer into a kind of zombie. At first glance it runs normally, but it works unnoticed as an attack bot — for example as part of a botnet to perform distributed denial-of-service (DDoS) attacks. This can flood websites or entire networks and bring them to a standstill.
- Spyware: Malware that snoops on you as you access your online accounts or enter your credit card information is called spyware. Hackers can then read your passwords and steal other sensitive data.
- Download Trojans: This type of Trojan targets devices that are already infected. It then downloads additional malicious modules, like ransomware, onto the device.
- Banking Trojans: They are among the most widespread Trojans. They aim to obtain the login details to your bank accounts using various phishing techniques.
- Fake antivirus programs: Trojans that disguise themselves as antivirus programs are super sneaky. They warn users about an alleged infestation and demand money to remove it. This scareware aims to confuse users. If you enter your payment details, cybercriminals can gain access to these details and misuse them.
- SMS Trojans: They infect mobile devices and can send and intercept texts. They often also send messages to premium rate numbers, sending your phone bill soaring. Even in the age of messaging services, these Trojans are still widespread.
These are just a few common examples of Trojans — there are many more and their number is growing, with cybercriminals constantly developing new ways to harm others and profit financially.
How do Trojans affect mobile devices?
In addition to laptops and computers, Trojans also target smartphones and other mobile devices like tablets. Similar to the desktop variant, the malicious code is hidden inside seemingly legitimate-looking apps. However, these are simply fake versions of apps that are infected with malware. Hackers usually place them on unofficial app stores. If unsuspecting users install them, their device gets infected.
Cybercriminals can then steal your data. You can also generate an income for cybercriminals through SMS Trojans by sending costly texts. Trojans can appear on both iPhones and Android devices. The Switcher Trojan is aimed at the latter. It also uses the device to attack the wireless network, allowing hackers to forward data traffic from other Wi-Fi-enabled devices.
Important to know: To protect yourself from an attack, it’s important to understand what a Trojan does and what the tell-tale signs are of an infection.
Spotting Trojans: What are the giveaways of an infestation?
Victims often fail initially to spot the signs of a Trojan attack. However, your alarm bells should be ringing if you notice the following symptoms on your device — regardless of whether it’s a desktop PC or a smartphone.
- New app: If a new app appears in the start menu that looks unfamiliar to you, this could be a sign of a Trojan infection.
- Bogus security warning: If pop-up windows with security warnings about viruses open in your browser, be suspicious and never click any links or respond to any requests for payment.
- Unexpected screenshots: If you find screenshots on your device that you didn’t take yourself, your computer or smartphone may be infected with a Trojan. The same applies if audio files start playing or photos begin displaying by themselves.
- Slow internet connection: If your internet connection suddenly grinds to a snail’s pace and becomes unstable, this may indicate a Trojan or other malware infection.
- Sudden reboot: If your computer reboots unexpectedly, this could also be a sign of a Trojan infection.
If you suffer any of the symptoms we’ve mentioned, use an antivirus tool right away to scan your device.
By the way: You can enjoy real-time protection against computer viruses and malware such as Trojans with Avira Free Security. You can then surf more safely, protected from cyberthreats.
How can I get rid of a Trojan?
If you spot a Trojan on your device, act quickly. The easiest way is to use an antivirus tool. Most versions can detect malware and remove it safely. If you’d rather remove the Trojan yourself, here’s how — with instructions for a range of devices.
Removing a Trojan from Windows 10 or 11
The best thing to do is restore your computer to an earlier point in time using System Restore. Choose a time when you are sure that the Trojan was not yet on your PC. If that doesn’t help, you should reinstall Windows. That ensures that all traces of data are deleted, including the Trojan. Before you do, back up all your important files first, such as to the cloud, a USB stick, or an external hard drive.
Removing malware from a Mac
Trojans often create new profiles to access your system or browser settings. So, first check whether a new profile has been added and then remove it. Also take these steps:
- Remove malicious apps: If you discover a malicious app, immediately move it to the Trash folder and empty it. Then check the library to see if there are any files associated with the app you just removed. If so, delete them as well. Empty the Trash folder again and restart your Mac.
- Reset your browser settings: Trojans often change your browser settings. As such, reset them to the default settings to remove the malware.
- Remove browser extensions: One possible source of a Trojan infection can be malicious browser extensions. Therefore, you should remove them immediately.
Removing Trojans from Android phones — even for free
First start your smartphone in safe mode. Typically, you do this by holding down the power button for a few seconds and then tapping the power off icon. You should then be prompted to start your device in safe mode. If you no longer suffer any issues after restarting your device, malware may have still infiltrated your Android smartphone via third-party apps.
If so, the next step is to check your downloaded apps. Uninstall apps you don’t recognize and those you downloaded shortly before the issues started. If that doesn’t help, reset your device to its factory settings to remove malware such as a Trojan from your Android phone. This also removes other types of malicious software. However, back up all your important files beforehand — such as to the cloud.
Finding and removing Trojans on an iPhone
If you spot a Trojan on your iPhone, remove it as soon as possible. The best way to do this is to turn off your device completely and then restart it. Then check if a new system update is available and install it. This is so important as Trojans often exploit vulnerabilities in older versions. Finally, delete your browser history and browsing data.
Do apps seem suspicious to you or don’t you remember ever downloading them? If so, remove them immediately. The same applies to apps you don’t use. You can also restore a previous backup version of your iPhone that wasn’t infected with a Trojan or other malware. If that doesn’t help, reset your device to factory settings after backing up your data.
How can I steer clear of a malware infection?
To infiltrate a system, Trojans rely on users downloading and executing them. Most malware infections can be avoided by keeping alert. Be skeptical of unknown websites that offer free apps, movies, or music. Also, never download free programs from third-party providers — only directly from the publisher. Here are some more handy hints:
- Update your software: Keep your operating system software up to date — the same goes for all your applications. That’s because outdated versions often contain security holes that cybercriminals exploit.
- Use a firewall: To connect securely to the internet, use a firewall. That’s because many firewalls can filter out malicious traffic themselves.
- Check email attachments: Be skeptical of unknown attachments or links in emails and, if in doubt, never open them.
- Create complex passwords: Complex passwords alone won’t protect you if your device is infected with a Trojan. However, these can make it more difficult for hackers to access your data.
It’s also a good idea to install an antivirus solution on your device.
Avira Free Security contains numerous protection features. Thanks to cloud-based detection of the latest threats, the tool detects Trojans and other malware in real time. It also comes with a password manager so you can generate unique passwords for each of your accounts. What’s more, you can surf more anonymously thanks to the built-in VPN.