How to Check Whether Your Computer Has Malware

James Frew 11-12-2017

We’ve all experienced that groggy feeling where your head is pounding, your nose is blocked, and you think you’ve developed the worst cough in history. Our bodies struggle through the day, when all we really want to do is watch Netflix under a duvet in a dark room. Fortunately our bodies are pretty adept at battling off those infections — even if we do have to spend a few days not feeling our best.


The symptoms of your latest illness could be indicative of a number of different health issues. Similarly, a computer virus can throw up symptoms which could be indicative of a range of different problems. While each symptom on its own may not trigger any red flags, a handful of unexpected behaviors may set off alarm bells — if you know what to look out for.

Here are some telltale signs that your PC has a computer virus.

1. Your Browser Starts Misbehaving

Popups were the scourge of the mid-2000s. The incredibly irritating screen hogs were often associated with internet Explorer, and became synonymous with malware lurking on your computer. Of course, these days a popup may just be a particularly annoying advert. However, if you are getting popups even when your browser isn’t open, then it might be a sign that all is not well. Many of these malicious popups will be for fake antivirus software or alerts that your machine is infected.

Popups aren’t the only indicator of concealed malware. If you find unexpected toolbars cluttering your browser 4 Annoying Browser Toolbars and How to Get Rid of Them Browser toolbars just don't seem to go away. Let's look at some common nuisances and detail how to remove them. Read More , that’s often evidence something’s amiss. Most browsers allow you to search from the address bar, and it often defaults to Google. If your search provider has suddenly changed, or your Google search results look unusual How to Easily Remove A Browser Redirect Virus You ran a search in Google, but somehow, for some reason, you didn't get the result you wanted after clicking a link. You're got a redirect virus; here's how to get rid of it. Read More , then you can be fairly certain you have an unwelcome intruder.


2. Your Antivirus Is Disabled

If someone wanted to break into your home, then one of the best ways of entering undetected would be to deactivate your home security system. The same is true of a computer virus. Some forms of malware are able to disable your antivirus software’s service, giving it unfettered access to your device. If the service is disabled, or your preferred antivirus software Top Free Antivirus Apps Without Nag Screens and Bloatware Nagging antivirus apps are a huge pain. You don't have to put up with them, even for free. Here are the best antivirus programs that don't come with popups or bundled junk. Read More is unable to update, then it’s time to start battling the infection Easily Remove Aggressive Malware With These 7 Tools Typical free anti-virus suites will only be able to get you so far when it comes to exposing and deleting malware. These seven utilities will weed out and remove malicious software for you. Read More .

3. Your PC Has Slowed to a Crawl

There are many reasons why your PC’s performance may slip over time How To Really Speed Up Your Computer - Common Myths & What To Do Instead Suffering from a slow computer? You might not know why and maybe you're trying to fix it in all the wrong ways. Let us help you with tips for a real speed boost. Read More . You should eliminate all the main suspects — including memory hogs like Chrome How to Reduce Google Chrome's Memory Usage and Free Up RAM Is Chrome using too much memory? Our tips will limit and reduce Chrome's memory usage to free up RAM. Read More — and check that all your hardware is in good working order 13 Windows Diagnostics Tools to Check Your PC's Health Use these computer diagnostic tools to run a PC health check and fix issues. Some support Windows 10 diagnostics, specifically. Read More . If you find everything to be functioning as expected, but your device is still slowing down, then it’s a good indicator of a malware infection. Malware can run applications and services in the background that clog up your computer, and can have an incredibly detrimental affect on your computer’s performance.

4. Your Files Are Disappearing

In recent years, one of the most devastating trends has been the rise of ransomware Is Ransomware Really as Terrifying as You Think? Ransomware is a regular nuisance. A ransomware infection takes your computer hostage, and demands payment for release. Often, payment doesn't secure your personal files. But is it really as terrifying as you think? Read More . This infection encrypts all your files, putting them beyond reach. The only way to unlock them is to pay the ransom, often in Bitcoin, but without a guarantee that they will be unlocked. The time between infection and encryption is often short, so the best defense is backing up your files regularly The Windows Backup and Restore Guide Disasters happen. Unless you're willing to lose your data, you need a good Windows backup routine. We'll show you how to prepare backups and restore them. Read More .


The best advice if you become infected with ransomware is to not pay the ransom. Other forms of malware can also lead to your files going errant. This can often be harder to detect, as you probably only notice once you need to open the file. However, if large chunks of data are missing then you should start scanning for a computer virus.

5. You Have Trouble Connecting to the Internet

If you suffer from poor network connectivity, then errors connecting to the internet are probably a regular occurrence for you. However, if they start fairly suddenly, or in conjunction with any other unusual behavior, then it may well be a symptom of a viral infection. You may think it seems strange that the virus would want to block your connection to the internet.

However, some malware changes your network settings to add a proxy and block your access to the internet How to Block Internet Explorer From Accessing the Internet Wondering how to disable Internet Explorer? Here's how to block Internet Explorer from accessing the internet and remove it. Read More to prevent you downloading tools to remove the infection. The best way to tackle this type of attack is to download a malware removal tool like Malwarebytes on another computer and transfer it to the infected machine via USB.


6. Programs Are Crashing All the Time

Programs can crash for a whole host of reasons 7 Most Common Reasons Windows Gets Unresponsive Sometimes, Windows freezes up and hangs without much of an explanation. Next time you suffer from an unresponsive system, review these seven common causes of Windows hangups. Read More which often have nothing to do with malware. Fortunately, there are plenty of ways that you can close the offending app How to Force Close a Program Without Task Manager Wondering how to force close a frozen program on Windows? Here are several ways to force-close apps without the Task Manager. Read More and get back to enjoying your day. If the regular troubleshooting steps don’t make an impact, then there’s a high probability that malware has something to do with it. If you have been experiencing the Blue Screen of Death 11 Tips to Help You Fix the Windows 10 Blue Screen Error What is a blue screen in Windows? How do you fix blue screen errors? Here are several fixes for this common Windows problem. Read More (BSOD) with alarming frequency, then make note of the error code.

Often the BSOD can be caused by hardware issues, but if investigation comes up empty, then there’s a good chance that a computer virus may be to blame.

7. New Programs Appear Unexpectedly

While flicking through your installed programs, you unearth a few that you really can’t remember having installed. There’s a chance that these came from dubious but legitimate installers OpenCandy: The Reason You Should Never Just Click "Next" Clicking "next" repeatedly is the quickest way of installing apps on Windows - until you find you installed other programs on your computer without realizing it, thanks to OpenCandy. Let's do something about that. Read More . However, if they have suddenly appeared and you are confident you didn’t install them by mistake, then it could indicate an infection. Your antivirus normally identifies these as Potentially Unwanted Programs (PUPs) and will alert you to them. If you haven’t seen a notification from your security software, consider running a manual scan.


If nothing is found, then perform an internet search to see if anyone else has reported that application as a PUP.

8. You Can’t Access Windows Utilities

When something goes awry on our Windows computer, the first thing we reach for is Ctrl + Alt + Del — only this time, you find that nothing happens. You attempt to right click on the taskbar to open Task Manager instead. Still nothing. Maybe opening it from the start menu will help? No luck there either.

You try to open Control Panel, and even Command Prompt to no avail. It’s almost as if there is something preventing you from opening these Windows utilities — and it’s quite likely there is.

9. Your Hard Drive Is Out of Control

Last week you had a sizable 30 percent free space on your hard drive. Now, you have less than 5 percent. You haven’t downloaded any large files, or installed any new software, so where is this data coming from? The most likely answer is that malware is downloading files and storing them on your hard drive. Another indicator is excessive hard drive activity.

Alarm bells should be ringing if you aren’t running any programs, or accessing files and your hard drive is showing a lot of activity and getting a little on the warm side.

10. Your Accounts Are Sending Spam

If you’ve received an accusatory message from a friend asking why you would recommend them weight loss pills, you should be on high alert. Odd messages like these indicate the presence of malware — so long as you didn’t send these messages as a form of misguided advice. Viruses are designed to spread, and one incredibly effective way is to bombarded your friends and contacts.

Most people are now accustomed to ignoring messages about magical pills and surprise inheritances, however, the viruses are maturing. Phishing is more commonplace How to Spot a Phishing Email Catching a phishing email is tough! Scammers pose as PayPal or Amazon, trying to steal your password and credit card information, are their deception is almost perfect. We show you how to spot the fraud. Read More than these overt examples of spam, where the recipient is tricked into opening a malicious link or attachment. This is a very effective means of spreading the computer virus as people are often more trusting of messages and emails from people they know.

It’s Oh So Quiet

Everything we’ve described so far has been a visible symptom of an infection. However, not all malware, particularly sophisticated variants, will intentionally disguise themselves. This makes detection almost impossible. As the saying goes: “absence of evidence is not evidence of absence.”

Unfortunately all our digital devices misbehave from time to time. This means random app crashes or unexpected behaviour can be entirely unrelated to a malware outbreak. However, if after following common troubleshooting steps you still come up empty, then these symptoms can be a sign that you may have been infected:

  • Browser malfunctions and misbehaviours
  • Problems with your antivirus or security software
  • Sudden or unexpected device slowdown
  • Missing files
  • Internet connectivity issues
  • Frequent and unexplained program crashes
  • Potentially unwanted programs (PUPs)
  • Inability to access common Windows utilities
  • Unexplained hard drive activity
  • Spam originating from your email or social accounts

Viruses and other forms of malware are almost unavoidable these days. While Windows has traditionally been platform of choice for malware, Mac users beware: you are at risk too. The best you can do is be prepared and take sensible precautions.

Always run an antivirus — even on your smartphone Do You Need Antivirus Apps on Android? What About iPhone? Does Android need antivirus apps? What about your iPhone? Here's why smartphone security apps are important. Read More . Maintain regular backups so that if the infection is too hard to remove you can start over with minimal impact. Downloading apps from free software sites can be a dangerous game, so be sure to stick to reputable sites The Safest Free Software Download Sites for Windows Many software download sites are loaded with malware. We compiled websites you can trust when you need a free software download. Read More . The internet is full of incredible content, but it pays to know what’s behind the link 7 Free Antivirus Tools for Your Browser: Scan Links Before You Click Viruses, malware, phished websites. Online mousetraps are lying in wait for some poor sucker to click on, so their computer can be added to the collection of zombie computers spewing out spam. Read More before you make that click.

Have you ever spotted any of these warning signs? Did you have a computer virus or was it a false flag? What other signs are there? Let us know in the comments!

Image Credit: kmiragaya/Depositphotos

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  1. Gary Gemmell
    December 27, 2017 at 2:03 am

    Learn and keep your eye on services and task manager daily!

  2. Zhong
    December 14, 2017 at 3:53 am

    How about for Unix systems? It might not have obvious signs since if the malware is better coded, it'll hide itself behind normal activity.

  3. kp
    December 11, 2017 at 11:25 pm

    Computer keeps turning itself on since I added a Brother printer - mostly at night - the printer wakes up then wakes up the pc.