What is malware, what are its types and how to defend against it

What is malware

Malware stands for “malicious software” and is the name given to various viruses, spyware or ransomware (cryptolocker) that harm users, their data or devices.

Theterm malware implies malicious intent on the part of the creator of the software, as opposed to, for example, unintentional software bugs, which can also cause data loss or device damage.

In the past, malware was more accurately described using terms such as virus, Trojan, worm or keylogger. These terms have fallen out of fashion because they are too precise and are often used incorrectly in general use.

Different types of malware

Nowadays, most malware takes the form of a virus and is named differently according to its function. However, malware can also enter a system unintentionally through software vulnerabilities.

How malware spreads

Malware is classified according to how it spreads. Viruses and worms replicate on an infected computer, for example, by finding other computers on the same network with the same vulnerability.

But while worms are primarily designed to damage the network itself (e.g. by a DDoS attack), viruses cause damage to the user’s device.

Trojans do not replicate. Rather, the user is tricked into installing malware, for example through social engineering or phishing. A Trojan horse may be disguised as other software or may even be part of seemingly legitimate software and exploit vulnerabilities to install itself with minimal user interaction. Trojans can also be delivered as add-ons for popular software or as fake updates.

How malware works and what it does

Whether it is a worm, Trojan or virus, malware can be distinguished by its functions. Currently, ransomware, adware, spyware and scareware are the most common.

Ransomware (also known as cryptolockers)

Ransomware or cryptolocker is a type of malware that encrypts your files after successfully infecting your device. Ransomware makes all your personal files inaccessible and can even disable your entire computer. The software will demand payment to decrypt your storage, usually in prepaid cards or Bitcoins (or other cryptocurrencies). As ransomware has become highly profitable compared to other types of malware, it is typical for this type of malware to exploit many vulnerabilities.


Spyware refers to any malicious software that collects your data without your consent and may ship with free applications or infect your computer via a virus or Trojan horse.

Spyware can also be installed on your devices by someone trying to control you directly. Some spyware is designed to continuously collect data about your location, app usage, passwords, and contact list. The most common types of spyware are keyloggers, which record all your keystrokes, and screen-scrapers, which take screenshots of your device on a regular basis.


Before ransomware, adware was a common type of “less harmful” malware that made money for itself by displaying advertisements to the user, for example in the form of a browser toolbar.


Another type of malware is scareware, which does not actually harm the user’s device. Instead, it attempts to scare the user into buying an expensive subscription in order to remove a non-existent or hypothetical threat. Most of today’s antivirus solutions can be considered scareware.

How to protect yourself from malware

There are three simple steps you can take to protect yourself from malware:

1. Always update your device

Viruses and many Trojans rely on software bugs and vulnerabilities to spread. Install patches whenever they are available and, if possible, enable automatic updates on your device.

2. Always verify the source of the software before installing

Protect yourself from malware bundled with software by downloading it only from the official source and verifying the integrity of the software, for example by checking its hash or PGP signature.

3. Use a firewall

Your personal computer should never receive incoming connections. A simple firewall should be installed on your computer and you should not turn it off. If you are behind a router, you probably also have some firewall privileges. Running a VPN on your computer will also act as a firewall.

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