Malware refers to any type of malicious software that attempts to infect a computer or mobile device. Hackers use malware for various reasons, such as extracting personal information or passwords, stealing money or preventing owners from accessing your device. “Malware” is a general term used to refer to a variety of forms of hostile or intrusive software.
It is not always easy to know if your computer was compromised or not, because these days cybercriminals do everything possible to hide their code and hide what their programs are doing on an infected computer.

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It is very difficult to provide a list of symptoms characteristic of an infected computer because the same symptoms can also be caused by hardware incompatibilities or system instability, however, here are some examples that may suggest that your PC has been compromised :

• You may receive the error “Internet Explorer could not display the page” when attempting to access certain websites.
• Your web browser (e.g., Microsoft Internet Explorer, Mozilla Firefox, Google Chrome) freezes, hangs or is unresponsive.
• Your web browser’s default homepage is changed.
• Access to security-related websites is blocked.
• You get redirected to web pages other than the one you intended to go to.
• You receive numerous web-browser popup messages.
• Strange or unexpected toolbars appear at the top of your web browser.
• Your computer runs slower than usual.
• Your computer freezes hang or is unresponsive.
• There are new icons on your desktop that you do not recognize.
• Your computer restarts by itself (but not a restart caused by Windows Updates).
• You see unusual error messages (e.g., messages saying there are missing or corrupt files folders).
• You are unable to access the Control Panel, Task Manager, Registry Editor or Command Prompt.

Malware includes computer viruses, ransomware, worms, Trojans, rootkits, key-loggers, dialers, spyware, adware, malicious BHOs, fraudulent security software and other malicious programs; most active malware threats are usually worms or trojans instead of viruses.
Below you can find a brief description of the most common types of malware:

Trojan Horse

A Trojan horse is a type of malware that claims to be useful, useful or fun, while actually causing damage or stealing data. Trojans often download other malicious programs (for example, spyware, adware, ransomware) also on an infected device.

Worm

A computer worm is a type of Trojan that is capable of spreading or replicating from one system to another. You can do this in several ways. Unlike viruses, worms do not need a host file to get stuck. After arriving and running on a target system, you can perform various malicious tasks, such as removing other malware, copying to devices physically connected to the affected system, deleting files and consuming bandwidth.

Spyware

Spyware is a type of malware that is difficult to detect. It collects information about your browsing habits, browsing history or personal information (such as credit card numbers) and often uses the Internet to pass this information to third parties without your knowledge. Keyloggers are a type of spyware that controls your keystrokes.

Ransomware

Rescue ransomware or malware is a threat that prevents users from accessing their personal or system files and demands a ransom payment in order to regain access.
Rootkits
The term “rootkit” comes from “rootkit”, a package that grants the highest privileges in the system. It is used to describe software that allows the stealthy presence of unauthorized functionalities in the system. Rootkits modify and intercept the typical modules of the environment (OS, or even deeper, bootkits).

Adware

Advertising software, short for advertising compatible software, is possibly the precursor to the modern PUP (potentially unwanted program). In general, advertising software is a standalone program that shows advertisements to the end-user in a variety of ways: within the program itself, or through pop-up windows, slider ads, pop-up browser windows, inserted advertisements or altered content on the website. The revenue generated by the ads is how the program to which the adware is linked is paid, which means that the end-user receives their desired tool or service for free.

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