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How to Tell if Your Computer Is Infected with Malware


The continuous increase in the number of people who use the internet has given birth to a new brand of criminal, the cyber criminals, and they keep coming up with new and innovative ways to scam and steal from the internet user. As the population has become extremely dependent on the internet, from conducting business to buying groceries, a massive growth in cyber-criminal activities and improved malware has become evident throughout the world.

With no shortage of ways and means to exploit unprotected computer systems, it is essential that we are aware of the major security threats and malware infections and are able to recognize them so that measures can be taken to protect and defend our privacy and sensitive information.

In this article, we will discuss how to determine if your system has been infected by malware, the correct ways of evaluating the risk, and the best places to look in for a solution.

Symptoms that determine your device has been infected

Internal processes slowing down

Ransomeware on your devices

The most common affect a virus or malware will have on your system is that it will slow down the speed of your internet connection, and that of the internal processes and applications. You may witness that your system takes longer to boot up, and that your applications take longer to execute.

If you feel your system is responding slower than usual, and you are not running any programs that may require a lot of resources, investigate other possible causes first. It could be that you do not have sufficient RAM, or space on your hard drive, or maybe a hardware malfunction that is affecting the performance of your system. It is advisable to run the system troubleshooter, and if the problem persists, refer to this to further investigate the causes for system slowdown.

If you have carefully investigated all the possible causes for a system slowdown and everything seems fine, you can begin considering the possibility that your system has been affected by malware.



If unwanted windows keep cropping up on your screen persistently, it is typically a sign that your system may have been affected by spyware. These pop-ups are an annoyance because not only do they hinder you from navigating the internet, they are extremely hard to get rid of, and keep cropping up no matter how many times you press the close button.

Apart from being infuriatingly annoying, these pop-up are often concealing malware threats which could prove to be far more devastating for your system.

The following practices should become a part of your internet surfing habits if you wish to avoid spyware infections:

  • avoid clicking on any pop-up windows that look suspicious or are from an unverified source
  • do not download any attachments from, or respond to any emails if you don’t recognize the sender
  • only download applications from trusted websites and sources

Since spyware threats are persistent and root themselves deep within your system, you will need a very good anti-spyware application to remove them. A few applications that have been found to be affective in removing spyware are Spybot Search and Destroy, Malwarebytes, and Ad-Aware by Lavasoft.

Unexpected system crashes

Crash report

If your system has been affected by malware, it may result in applications crashing constantly, your system freezing up, or crashing continuously to show the much dreaded Blue Screen of Death. All these are evident signs that your system is not functioning properly and you should investigate what the source of the problem is. It could be one of the following two things:

  • It could be a technical issue resulting from your hardware or software being incompatible with your operating system, or could be caused by a lack of system memory
  • Or it could be malware affecting your system

A software may crash or may cause the system to crash if it is conflicting with other programs that you are running. Any corrupt or stray registry keys may also cause your system to malfunction and crash.

If it isn’t any technical issues that are causing your system to crash, and you suspect malware involvement, run a full scan of your system using an antivirus program. If you are using a Windows 8 operating system or newer, you can use Microsoft’s in-built anti-virus system for this purpose. Alternatively, you can download a trusted malware protection software like AVG from a safe source. A good antivirus application will regularly update their virus database, and incorporate real-time protection, and firewall capabilities.

Refer to reviews and antivirus benchmarks carried out by reputable sources like PC Magazine, Virus Bulletin, and AV Comparatives to select the best antivirus program for you.

Excessive ghost-activity on the hard drive

Ghost activity

Your system may be affected by malware if you notice continuous activity on your hard drive even when you’re not using it, downloading anything from the internet, or running an application. It is advisable to get a trusted antivirus application to scan your system for malware at this point.

It is also worth a mention that unusual hard-drive activity may, in some cases, may be caused by a hardware malfunction or a damaged hard-drive. So if the antivirus scan does not reveal any threats, this should also be considered.

Unusual and excessive consumption of hard drive space

Wannacry ransomeware

Sometimes you may find that free space in your hard drive is reducing or that it has become completely full even though you haven’t saved or installed any programs on it and it looks visibly empty. You may also notice some files or folders that you did not create, or that some files you saved have disappeared or are behaving unusually.

This could be a sign that your system has been affected by malware as some of them fill up your hard drive through various means until it crashes.

Disappearing files and folders could also signify a malfunctioning hard drive, which should also be considered.

High network activity

High Network Activity

If you observe strange or high network activity even when you are not downloading anything from the internet, surfing the internet through your browser, or using any application that connects to the internet, you may want to check if:

  • the Windows is updating in the background
  • any of the installed applications, like cloud backup software, are downloading or uploading any data
  • any application is running an update process in the background
  • you forgot about any downloads that you minimized to the system tray and forgot about

If you determine that none of the above apply, then you should investigate the source of all the excess traffic. You could:

  • Monitor your network through a trusted third-party network monitoring software like Wireshark, GlassWire, or Little-Snitch.
  • Run an antivirus application to check for a malware and make sure to use a trusted antivirus application to do so.

Some malware threats, like financial malware, may be exceptionally malign and you may not be able to quarantine or delete them using a regular antivirus application. If you suspect your system has been attacked by such malware, you may need to use paid-for security suites that specialize in the removal of such malware to address the issue.

Changed browser homepage, appearance of toolbars you didn’t install, or your browser leading you to a different website than the one you had intended

New tabs

As the title above says, if you open your browser and notice that the homepage is different, or there are new toolbars at the top that you don’t remember installing, or your browser redirects you to suspicious pages even when you’re trying to access a trusted website, all these could be signs that a malware is behind it all.

Such malware gains access to your system when you visit a public-sharing website or one with an unverified source, and click on a pop-window or a link that you shouldn’t have clicked on. This downloads malicious software to your system in the background, the effects of which, can not only be annoying, but also devastating for your computer.

If you notice any of this happening, use your antivirus software to conduct a thorough scan of your system, and quarantine and delete any threats. Such threats may be malignant and persistent and may not go away with a regular antivirus software, in which case you will have to install a trusted and specialized security suite that is famous for dealing with such threats.

Warning messages or unusual program activity

Virus alert

If you observe any of these occurrences on your system, you should pay close attention and try investigating the root of the issue:

  • Applications automatically opening and closing when you are not using them
  • Sudden shutting down of the operating system without any reason
  • Suspicious windows opening and closing on your desktop during the booting process
  • Warning messages displaying that control of your hard drives has been lost

All the above may occur as a result of technical issues, in which case you should troubleshoot your system using Microsoft’s utility, but it could also signify the presence of malware on the computer. If the malware has limited your control over your operating system, to the extent that you can’t open, delete, or remove files or applications, or your operating system is malfunctioning, then the malware may have rooted itself deeply in your system and the best course of action could be to use a bootable CD or USB to format the hard drive and reinstall the operating system.

Antivirus software acting suspiciously

How to detect viruses

If the malware protection software you have installed does not execute, initiate system scan, or if the virus database updates have been suspiciously disabled, you should investigate the occurrence immediately.

The particularly notorious malware will target your antivirus system first and disable it, leaving you vulnerable to all threats. When faced with such an occurrence, your first course of action should be close the antivirus application and try opening it again, reboot your computer, or uninstall and reinstall the software. If doing this does not resolve the issue, it could mean the system has been affected by a malicious threat.

As malware is continuously evolving, some free antivirus applications may not be able to detect or take action against the particularly nasty ones like financial malware or ransomware, leaving your computer and your information completely vulnerable. To safeguard yourself against such threats, you should only use antivirus programs from reputable companies, or the ones designed by Microsoft, and keep the virus database updated.

Your contacts complain about getting suspicious messages from your account

Facebook messages

If your contacts tell you that they’ve received emails or instant messages from your account that are suspicious in nature and contain links or attachments, and you’re quite sure you haven’t sent any of the messages, you should investigate immediately.

Check your sent email folder in your email account to determine if the emails were sent from your account. If the Sent messages folder is empty, it means that the messages were sent using your email from a third-party application, and this is out of your control. If it isn’t empty and there is a record of all the sent messages that you didn’t send, your account has most likely been hacked and you should change your password immediately. To ensure this doesn’t happen in the future, form a habit of taking the following steps:

  • Logout from your internet account after your work is done, especially if you’re accessing it on a public network or from the workplace. Even if you are using the account on a trusted network, it is still an advisable practice to log out after every use, and make sure to log out from all devices like your computer, laptop, and mobile phone.
  • Regularly change your passwords and use strong passwords that contain a combination of letters, numbers, and other characters if allowed. Using one password for all your accounts is also an unadvisable practice. This is particularly if you are hacked, in which case all your accounts will not be compromised at once.
  • Most high-security accounts today provide the option for multiple-step authentication, which can be enabled from the settings. When it is enabled, if your account is accessed from a new device, you will be required to enter your password, and an authentication passcode sent to your phone or a designated email address. This options makes your account more secure and gives your peace of mind as you know all new activity to your account has to be authorized by you.

Knowledge determines the best course of action

Being aware of the most common malware activity and its symptoms is the first step towards protecting and defending yourself against it. The extent of your knowledge regarding the issues determines whether you get surf the dark waters of the internet with safety, or get your identity stolen by cyber-pirates.

Merely installing an antivirus program, or purchasing a security suite and believing it will ensure your safety is naive, as no protection is infallible. Therefore, knowledge of how malware behaves on the computer can enable you to put safeguards in place for all possible vulnerabilities, or at least recognize its symptoms in time to take effective measures to limit its effect.

Still searching for more? Then learn 13 ransomware prevention tips and 8 cyber security facts that affect your online safety.