There are some common signs that may indicate your computer has been infected with malware maybe from adware, spyware, trojans, viruses or some other form of exploitation. Although malware covers a broad category of software that is designed to damage and operate against a user’s intent, its symptoms are easily recognizable to the average user.

10 Common Symptoms of Computer Viruses

1. You are the only user on your computer but there are changes you did not make.

Common examples include knowing your homepage is different, there is a new toolbar that you didn’t install, favorites have been added to your browser, your default browser or search engine has changed, your default language has changed, and more.

2. Your computer stops running and slow.

Slowdown can be a sign of malware, especially if you don’t have network problems and haven’t downloaded large programs and don’t have multiple programs running at the same time. If you look at your task manager and there are all sorts of system resources being used for things you don’t do, you may be infected.

3. You start getting a lot of pop-ups.

One of the more common examples of malware is receiving advertisements even when you are not on the internet. A very bad variation is a popup advertisement that warns you that your computer is infected and directs you to click on the antivirus offered (that is fake) to protect your computer. Never click anywhere on this popup because any click will give you more problems. Instead turn off pop-ups through your task manager.

4. Files are missing or changed.

First, make sure you don’t misfile things, but if the file is missing or the author has changed, you may be infected. If you can see your files but can’t access them, you may have hostage software – malware that grabs access until you pay for extortion (don’t do it because you still won’t get access). This is another good reason to back up your files automatically every day.

5. Your computer is not performing basic functions.

Examples of basic functions that are symptoms of a malware infection include having a system that won’t boot, won’t connect to the Internet (or connect with a bunch of open windows to sites you don’t go to), won’t perform basic functions, be turned off randomly, or perform another weird thing.

6. Your computer sends an email that you did not generate.

You may be infected and may be part of a botnet. A bot is a type of software application or script written to perform automated tasks on commands. Bad bots allow attackers to take remote control over the affected computer. When a large number of bots take over a large number of computers, they form what are known as “botnets”, which give hackers huge computing power when collectively controlled.

7. You have an antivirus program but it is missing.

You may be infected especially if all your security tools are disabled or have been lost. Many malware threats target security systems first so that they can wreak havoc without being prevented.

8. You cannot open or run your application (or clicking on one app icon actually opens something else).

Combining or redirecting user actions for the purpose of performing other unintentional actions is a common technique among malicious hackers. This is their way of making sure they stay in control of your device or achieve other malicious purposes.

9. Typing a URL to a specific website takes you elsewhere.

This can be a very worrying sign when you are redirected to a site that looks similar, but is not exactly the same as the site you want to visit. This is a common tactic of Trojan viruses, which often originate from browser-based infections.

10. You haven’t noticed anything wrong with your computer.

Unfortunately, a lot of malware is specifically designed to go undetectable, so while the previous nine things are important to look for, you may be infected without knowing it.

Credit to: