10 Symptoms of a Computer Infected with Malware

Are you living in a perfect world? Your antivirus do not alarm you about any infections. Your firewall probably don’t even alarm you as well about intruders. Is this how you defined SAFE?

If I were you, I would not. Personally, I had tried before having an infection without my antivirus (Avast antivirus at that time) and my firewall (Windows Vista Firewall) alarming me about it. If you are not too sure about all these things, you might first want to check out my post on What is Computer Security.

How I know my computer is infected with Malware?

However, I scheduled a pre-boot scan using my Avast free antivirus and finally, I got the malware removed. How I know my computer was infected? Below are 10 symptoms which tells me that my computer is infected and would like to share to you all about my experience.

Note: Not all applied to my actual experience but all of the below are some of the basic items that you should diagnose.


1. Performance dropped when you are not doing anything heavy. Imagine when you are just playing solitaire and nothing else, really nothing else but you took over 30 seconds to shift your card from one side to another. Is that normal? You do feel something is wrong isn’t it? Probably some malware is working extremely heavy behind which you didn’t realize and you should do a check up.

2. Internet speed greatly reduced. Google home page does not take more than 10 seconds to load. If you are taking 30 seconds (again) to load just the Google Search Home Page, again, you should check up. This is because sometimes Malware will make use of your bandwidth to download things which you don’t need or even to upload your things to the host of the Malware. With that, your internet speed will be greatly reduced.

3. Unfamiliar error messages. If you did not install anything new to your system but start getting error messages which you don’t even can understand, it is also another sign of infection. This is one of my personal experience where there was once I kept getting an error during each start up. I run an antivirus scan but no Malware found. I run again during pre-boot and found one Malware which I managed to remove and the error stop popping out.

4. Web browser home page suddenly changed. When I was young, I love going to unknown sites to download cracked games. My action was paid off with plenty of Malware where it first changed the home page of my web browser. I then tried to manually set it back to auto-blank, Yahoo, Hotmail, but none work. It still reverting back to the home page that I don’t even know until I run the antivirus scan. At that time, it was Virus Buster and I am not too sure it is still available today.

5. You are seeing something that is not English. When you are seeing something which is not the usual language that you set, you might be infected with some Malware. This is because certain Malware are programmed to infect certain region only but you might be unlucky to get a share of it simply because you happen to visit those sites or downloaded those programs. Pay attention to the language and make sure you always see things that you can understand.

6. High CPU performance when your computer is idle. If you put your computer to idle and notice that it is still processing heavily, this means something is working very hard in your computer. Something which you don’t even know and most probably, that thing is going to be a Malware. It could also be a Super-Worm that keeps duplicating which uses your CPU resources. None of them are good and please get rid of them if you notice this scenario.

7. Blue screen for no reason. The best way for hacker to make Microsoft unable to return a proper Error Code is to force your Operating System to go Blue Screen. Notice that whenever your computer is attached with some issue and your Windows will automatically ask you whether you want to send a report to Microsoft. This could help Microsoft to track down the hackers attacking method and by turning it to Blue Screen, it mostly solves everything. I seen quite a few times of Blue Screen and it usually returned the same error code.

8. Antivirus and firewall protection suddenly disabled. If your antivirus and firewall suddenly automatically disabled without asking you, most likely someone is not happy to be observed all the time. It is common today that a Malware can disable an antivirus protection. As a result, you should always check that your antivirus is working and running at full protection unless you say so.

9. Unnecessary files start duplicating. Worms, a form of Malware where it likes to duplicate itself or some files to annoy you. Worms used to be just annoying but not dangerous…I’m not too sure about Worm in 2012. But the most important thing here is, if you see unfamiliar files, start removing them. If they still appear few hours or days later, start scanning your computer because it is not going to be normal anymore.

10. Your friends started to call you. This is pretty straight forward. When your friends start calling you and ask you to stop spamming them via emails, you know what had already happened to you. Start off by creating a strong password and start scanning your computers again.


What about you? Do you have anymore symptoms apart from the ones mentioned above based on your experience? Do share with us below. I had written a post on how to remove virus and you might want to check it out if you had one of those symptoms.

Image Credit: Castillo Dominici

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  3. 10 Ways to Get Your Computer Infected With Malware
About Alan Tay

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  1. Peter Lee

    Great tips Alan! I never thought of #6 where the CPU is still running heavily when idle that it could be a sign of malware attack. I’ve learned a new thing from you today 🙂 Recently #10 hit me. A few of my friends called and told me that they’ve received emails “from me” asking them to click a link which will entilte them a 50% discount on Rolex watches (Incredible!!!). Even I myself received the emails, sent from and to the SAME EMAIL ADDRESS (Perfect!!!). Luckily all my friends are not that stupid to believe in such nonsense.
    Peter Lee recently posted..How To Maintain Security At The OfficeMy Profile

    • Alan Tay says:

      Your friends are aware of computer threats very well. Good for your friends 😉

      In fact, there could be many more symptoms, probably other readers will contribute and we will see 😉

    • Tan

      My colleague also keep on send me and the rest of our colleagues this kind of email, but can’t remember what exactly. This problem solve until I remind him to change his msn password.

      • Alan Tay says:

        Ahh, that is quite a common issue. A lot of people have this problem. I think the best is we don’t click on those links that they sent to us.

  2. Tan

    Additional symptoms here:-
    File extension or files being set to invisible without your knowledge.
    Hand disk drive free space indicate wrongly or suddenly out of space.

  3. reya says:

    I rarely experience with virus infected is using security software, using a private internet connection and only using one USB if you want to enter data into the PC … maybe this tips from me and hopefully useful
    reya recently posted..Antivirus Solutions – K7 Total Security Software For Mac OS & Windows OSMy Profile

  4. Easy Tips says:

    The computer can also restart frequently when infected.
    Easy Tips recently posted..Airtel 4G Tariff Plans, Download And Upload SpeedMy Profile

  5. Becca says:

    Another useful tips Alan. I experienced in old pc my firewall was suddenly disabled which very rarely
    to happen. And do not know what is the cause. thanks for the reminder.

  6. Jeff from PC Enthusiast

    That is one of the reason why I like everything in my system is modular.
    The system files are isolated in one hard drive and all other stuffs are located in another hard drive. Because when things like this happens and even virus removal software could not remove the malware, I just reformat and reinstall the whole system again. ^_^
    Jeff recently posted..Diablo III Player Earned $10K from RMAH. For Real?!My Profile

  7. Ryan Cruise

    You can never be really 100% SAFE and AVOID Malware problems, unless you don’t connect to the internet. Sometimes you’re just browsing and you end up clickinon ads that are disguised as not ads. I have experienced that using MAC and Linux OS lessened malware infectioins.

    Hopefully the PC platform will have the security of this UNIX based OS and still be as flexible as the PC platforms.

    Ryan Cruise recently posted..Diablo 3 Gold Secrets – ImportantMy Profile

  8. Chris says:

    Another symptom is getting annoying popup messages warning that your computer is infected. The messages are the malware. If you see that your internet connection is not working, the malware may have changed your internet connection settings to “use proxy server”. This will kill your connection, and it is a sign that you have malware. I’ve had good success using malwarebytes to find and remove malware.
    Chris recently posted..Petition to Save the Hope ScholarshipMy Profile

  9. Suresh Gupta says:

    Nice and Great tips Alan!Virus infected is using security software, using a private internet connection and only using one USB.Because when things like this happens and even virus removal software could not remober on pc.

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