Malware, Trojans and Ransomware – How to Protect Yourself

Cyberattacks against companies and private individuals are increasing rapidly. Behind many of the most damaging attacks are different types of malicious software that can steal data, lock systems, or give attackers control over your devices. But what is the difference between malware, Trojans and ransomware? And how can you protect yourself against these threats?

 

What is malware?

Malware is short for “malicious software”, meaning harmful software. It is a collective term for all types of software designed to damage, steal information or gain unauthorised access to computers and networks.

The term malware is most often used as an umbrella concept that includes many different types of threats. Viruses, Trojans, ransomware, spyware and worms are all examples of different forms of malicious software. Each type has its own characteristics and methods of spreading and causing damage.

How does malware work?

Malicious software can enter your system in several different ways:

Via email and attachments

The most common distribution method is phishing. You receive an email that appears legitimate, perhaps from a bank or government agency, with an attachment or a link. When you open the attachment or click the link, the malicious software is installed.

Through downloads

Malware can be hidden in programs you download from the internet. This can include pirated software, fake updates or even legitimate programs that have been infected.

Via infected websites

Some websites are specifically designed to spread malicious code. Simply visiting the site can result in software being installed on your computer, especially if your browser or operating system has security vulnerabilities.

Through USB drives and external devices

Malicious software can also spread via USB sticks and external hard drives. If you connect an infected device to your computer, the software may spread automatically.

Via networks

In corporate environments, malware can spread through local networks. If one computer becomes infected, the software can search for other vulnerable devices on the same network.

What can malware do?

Depending on the type, malicious software can have different purposes:

• Steal sensitive information such as passwords, credit card numbers and personal data
• Encrypt files and demand a ransom (ransomware)
• Give attackers remote control of your computer
• Use your computer to attack other systems
• Spy on your activity and record keystrokes
• Send spam or spread further malicious code to your contacts
• Destroy or delete data
• Hijack system resources to mine cryptocurrency

 

Trojans – the fake package

A Trojan, or Trojan horse as it is also called, is a type of malware that disguises itself as something legitimate. The name comes from the Greek myth of the Trojan Horse, which appeared to be a gift but hid soldiers inside.

How does a Trojan work?

A Trojan differs from a virus in that it does not spread on its own. Instead, it tricks the user into installing it by appearing to be something useful or desirable. This could be:

• A free tool or game
• A software update
• A document in an email message
• A video file or image

Once you install or open the file, the Trojan is activated and begins its destructive work in the background, often without you noticing.

Different types of Trojans

Backdoor Trojans

These create a backdoor in your system that gives attackers remote access. They can then install more software, steal files or use your computer for illegal activities.

Banking Trojans

Specialised Trojans designed to steal information about bank accounts and payments. They can record keystrokes when you log into your bank or take screenshots of sensitive information.

Downloader Trojans

These Trojans are primarily designed to download and install additional malicious software onto your computer. They act as an entry point for more advanced attacks.

DDoS Trojans

These hijack your computer and use it as part of a botnet to carry out DDoS (Distributed Denial of Service) attacks against websites or services.

Spyware Trojans

They monitor your activity, record keystrokes, take screenshots, and can even activate your webcam or microphone without you noticing.

Warning signs of Trojans

It can be difficult to detect a Trojan, but here are some signs that may indicate an infection:

• Your computer suddenly becomes much slower
• Programs start or close by themselves
• Strange error messages appear
• Network activity even when you are not using the internet
• Antivirus software or firewall turns off without your permission
• New programs or icons you did not install appear
• Your browser redirects you to unusual websites

How to remove Trojans

If you suspect that your computer is infected with a Trojan, it is important to act quickly.

Disconnect from the internet

First and foremost, disconnect your computer from the internet to prevent the Trojan from communicating with attackers or spreading to other devices on the network.

Start in Safe Mode

Restart your computer in Safe Mode. This starts Windows with minimal programs and makes it easier to find and remove malicious software.

Run antivirus software

Use an up-to-date antivirus program to scan your system. If you do not already have one installed, you can download one from another secure computer and transfer it via USB.

Use specialised tools

There are tools specifically designed to remove Trojans. Malwarebytes and Kaspersky offer free tools that can often detect and remove threats that standard antivirus programs may miss.

Restore the system if necessary

If the Trojan is deeply embedded in the system, you may need to restore Windows to a previous point in time or perform a clean reinstallation of the operating system.

Change all passwords

After the Trojan has been removed, change all important passwords from a different, secure device. Start with banking, email and other sensitive accounts.

 

Ransomware – when your data is held hostage

Ransomware is a particularly malicious form of malware that encrypts your files and demands a ransom to unlock them. In recent years, ransomware attacks have increased dramatically, especially against companies and government agencies.

How does ransomware work?

When ransomware enters your system, it begins systematically encrypting your files. These can include documents, images, databases and other important files. The encryption uses strong cryptographic methods that make it virtually impossible to recover the files without the decryption key.

After the files have been encrypted, a message appears on the screen explaining that your files are locked and how much you must pay to get them back. Payment is almost always demanded in cryptocurrency such as Bitcoin, as it is harder to trace.

Types of ransomware

Crypto ransomware

The most common type, which encrypts your files. Examples include WannaCry, Locky and CryptoLocker. These are particularly dangerous for companies because they can spread across entire networks and encrypt systems.

Locker ransomware

Instead of encrypting files, this type simply locks the user out of the computer. You cannot access the operating system at all. These are generally less severe because the files are not encrypted and they can often be removed more easily.

Scareware

Fake security programs that claim your computer is infected and demand payment to “fix” the problem. Technically less harmful, but they can still trick users into paying money.

Doxware eller leakware

This type not only threatens to encrypt data but also to publish sensitive information if the ransom is not paid. This is especially serious for companies handling sensitive customer data.

Known ransomware attacks

WannaCry (2017)

One of the largest ransomware attacks ever, affecting over 200,000 computers in 150 countries. The attack exploited a vulnerability in Windows and spread rapidly across networks. Among those affected was the NHS in the United Kingdom, where hospitals were forced to cancel operations.

NotPetya (2017)

Primarily targeted Ukrainian companies but spread globally, causing damages worth billions. Many experts believe this was a state-sponsored cyberattack rather than a purely criminal, profit-driven attack.

REvil/Sodinokibi

A ransomware-as-a-service group used in several high-profile attacks, including those against meat producer JBS and IT company Kaseya. The attacks on Kaseya indirectly affected thousands of companies.

Should you pay the ransom?

Authorities and cybersecurity experts strongly advise NOT to pay the ransom for several reasons:

• There is no guarantee you will get your files back even if you pay
• You are funding criminal activity and encouraging further attacks
• It makes you a known target for future attacks
• In some countries, laws prohibit paying ransoms to criminal organisations

Instead, you should:

• Immediately disconnect infected devices from the network
• Contact the police and IT security experts
• Restore systems from backups if possible
• Check whether free decryption tools are available (NoMoreRansom.org collects such tools)

How to protect yourself against malware

Protection against malware requires multiple layers of security. No single measure is sufficient on its own.

Basic security measures

Keep systems updated

Always install security updates for your operating system, programs and apps. Many malware attacks exploit known vulnerabilities that have already been fixed in updates.

Use antivirus software

A good antivirus program can detect and block much malware before it has a chance to run. Make sure the software updates automatically and performs regular scans.

Enable a firewall

Both Windows and macOS have built-in firewalls. Make sure they are enabled. In corporate environments, more advanced network firewalls are often required.

Be cautious with email

Do not open attachments or click links from unknown senders. Even if the email looks legitimate, carefully double-check the sender’s email address. Phishing emails can look very convincing.

Only download from trusted sources

Avoid downloading software from unknown websites or torrent sites. Stick to official app stores and manufacturers’ websites.

Use strong passwords

Strong, unique passwords for each service reduce the risk that a Trojan stealing passwords can gain access to multiple accounts. Use a password manager.

Backups – the most important protection against ransomware

The single most important measure against ransomware is regular backups.

The 3-2-1 rule:

• 3 copies of your data (the original plus two backups)
• 2 different types of media (e.g. hard drive and cloud)
• 1 copy offsite (physically separated from the original)

Important: Make sure backups are not permanently connected to the network, otherwise ransomware may encrypt them as well.

Training and awareness

Humans are often the weakest link in the security chain. Train staff on:

• What phishing attacks look like
• The importance of reporting suspicious emails
• Secure procedures for handling sensitive information
• How to recognise warning signs of malware

Advanced protection for businesses

Network segmentation

Divide the network into different zones so that malware cannot spread freely across all systems if one device becomes infected.

Endpoint protection

Advanced security solutions that monitor and protect all endpoints (computers, servers, mobile devices) in real time.

Email filtering

Solutions that analyse emails and block suspicious messages before they reach the user’s inbox.

Incident response plan

Have a prepared plan for what should be done in the event of a malware attack. Who should be contacted? How are infected systems isolated? How is the business restored?

Penetration testing

Hire security experts to test your systems and identify vulnerabilities before attackers find them.

What to do if you have been infected

If you suspect your system is infected with malware, act quickly.

Immediate actions

Disconnect from the network

Turn off Wi-Fi or unplug the network cable to prevent the malicious software from spreading or communicating with attackers.

Do not turn off the computer

In the case of ransomware, shutting down or restarting may trigger further file encryption. Leave the computer on but isolated.

Document

Take photos of error messages or ransomware notes. This can help security experts identify the type of malware.

Contact IT support or an expert

In companies, contact the IT department immediately. As a private individual, you may need to hire a security expert.

Report to the police

Especially in the case of ransomware, you should file a police report. This may also be required by insurance companies.

Removal of malicious software

Run antivirus software

Start your computer in Safe Mode and run a full scan with an updated antivirus program. Safe Mode starts Windows with minimal programs, making it easier to find and remove malware.

Use specialised tools

There are tools specifically designed to remove certain types of malicious software. Providers such as Malwarebytes and Kaspersky offer free removal tools.

Restore the system

In severe cases, you may need to restore the operating system to a previous point or perform a clean reinstallation. This is especially relevant if Trojans have created backdoors in the system.

Change passwords

After the malicious software has been removed, change all passwords. Start with the most important ones (banking, email) and do this from a different, secure device.

After the attack

Analyse how it happened

Try to understand how the malware entered the system. Was it through an email? A download? This helps prevent future attacks.

Improve security

Implement the security measures that could have prevented the attack. This may include better email filtering, stricter download policies or additional training.

Monitor systems

After an infection, closely monitor your systems for several weeks. Some types of malware can remain dormant or reappear.

Future threats

Malware is constantly evolving and becoming more sophisticated.

AI-driven malware

Future malicious software may use artificial intelligence to:

• Adapt to defences and find new ways to bypass security
• Personalise phishing attacks based on the victim’s behaviour
• Hide more effectively by learning how antivirus software detects threats
• Automatically identify vulnerabilities in systems

Attacks against IoT

With more connected devices in homes and businesses, the attack surface is increasing. Many IoT devices have weak security and can become entry points for malware into networks.

Fileless malware

This type of malicious software leaves no files on the hard drive and instead runs directly in the computer’s memory. This makes it much harder to detect using traditional antivirus solutions.

Supply chain attacks

Attackers infiltrate software companies and infect legitimate programs during development. When users download updates or new versions, they unknowingly receive malware.

Polymorphic malware

Malicious software that changes its code every time it spreads, making it very difficult for antivirus programs to recognise it based on signatures.

Protect yourself against tomorrow’s threats

Malware, Trojans and ransomware pose real threats to both companies and individuals. The cost of cyberattacks is increasing every year, not only in direct losses but also in lost productivity, reputational damage and expenses related to system recovery.

There is no such thing as 100% security, but by combining technical safeguards with awareness and good practices, you can significantly reduce the risk of being affected. Regular updates, antivirus software, firewalls and backups are the cornerstones of strong protection.

For businesses, it is also important to have a contingency plan. When an attack happens, it is too late to start deciding what to do. Have clear procedures in place, know who should be contacted, and how systems should be isolated and restored.

Remember that humans are often the weakest link. One employee clicking the wrong link can give attackers access to an entire corporate network. That is why ongoing training and awareness are just as important as technical solutions.

Cyber threats are constantly evolving, but by staying informed and taking the right measures, you can protect yourself and your organisation from most attacks. Invest in security today, so you do not have to pay the price of an attack tomorrow.